Book - History of embryology in Russia 1750 - 1850

Embryology - 19 Apr 2024        Expand to Translate
Google Translate - select your language from the list shown below (this will open a new external page)
العربية | català | 中文 | 中國傳統的 | français | Deutsche | עִברִית | हिंदी | bahasa Indonesia | italiano | 日本語 | 한국어 | မြန်မာ | Pilipino | Polskie | português | ਪੰਜਾਬੀ ਦੇ | Română | русский | Español | Swahili | Svensk | ไทย | Türkçe | اردو | ייִדיש | Tiếng Việt    These external translations are automated and may not be accurate. (More? About Translations)

Blyakher L. History of embryology in Russia from the middle of the eighteenth to the middle of the nineteenth century (istoryia embriologii v Rossii s serediny XVIII do serediny XIX veka) (1955) Academy of Sciences USSR. Institute of the History of Science and Technology. Translation Smithsonian Institution (1982).

Historic Russian Embryology 1955: 1. Beginning of Embryological Investigations Lomonosov's Epoch | 2. Preformation or New Formation? | 3. Kaspar Friedrich Wolff - Theory of Epigenesis | 4. Wolff: "Theory Of Generation" | 5. Wolff: "Formation of the Intestine" | 6. Wolff's Teratological Works | 7. Wolff: "On the Special Essential Tower" | 8. Ideology of Wolff | Chapter 9. Theory of Epigenesis End of 18th Century | 10. Embryology in the Struggle of Russian Empirical Science Against Naturphilosophie | 11. Louis Tredern - Forgotten Embryologist Beginning of 19th Century | 12. Embryonic Membranes of Mammals - Ludwig Heinrich Bojanus | 13. Embryonic Layers - Kh. I. Pander | 14. Karl Maksimovich Baer | 15. Baer's - De Ovi Mammalium Et Hominis Genesi | 16. Baer's Ober Entw I Cklungsgesch I Chte Der Thiere | 17. Baer Part 1 - Chicken Development | 18. Baer Part 2 - History of Chicken Development | 19. Baer Vol 2 | 20. Third Part of the Bird Egg and Embryo Development | 21. Third Part - Development of Reptiles, Mammals, and Animals Deprived of Amnion and Yolk Sac | 22. Fourth Part - Development of Man | 23. Baer's Teratological Works and Embryological Reports in Petersburg | Chapter 24. Baer's Theoretical Views | 25. Invertebrate Embryology - A. Grube, A. D. Nordmann, N. A. Warnek, and A. Krohn

Online Editor

This historic textbook by Bliakher translated from Russian, describes historic embryology in Russia between 1750 - 1850. Publishing House of the Academy of Science USSR Moscow 1955 Translated from Russian Translated and Edited by: Dr. Hosni Ibrahim Youssef # Faculty of Veterinary Medicine Cairo University Dr. Boulos Abdel Malek Head of Veterinary Research Division NAMRU-3, Cairo Arab Republic of Egypt Published for The Smithsonian Institution and the National Science Foundation, Washington, D.C, by The Al Ahram Center for Scientific Translations 1982 Published for The Smithsonian Institution and the National Science Foundation, Washington, D.C by The Al Ahram Center for Scientific Translations (1982) Also available online Internet Archive Historic Embryology Textbooks

Historic Disclaimer - information about historic embryology pages

Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Academy of Sciences USSR

Institute of the History of Science and Technology

A. N. Severtsov Institute of Animal Morphology

L. Ya. Blyakher

History of Embryology in Russia from the Middle of the Eighteenth to the Middle of the Nineteenth Century

(Istoryia Embriologii v Rossii s serediny XVIII do serediny XIX veka)

Institute of the History of Science and Technology

A. N. Severtsov Institute of Animal Morphology

L. Ya Blyakher

Editor: G. A. Shmidt

With an Introduction by Jane Maienschein

Publishing House of the Academy of Science USSR

Moscow 1955

Contents

Introduction by Jane Maienschein

Preface

1. The Beginning of Embryological Investigations in Russia in Lomonosov's Epoch
2. Preformation or New Formation?
3. Kaspar Friedrich Wolff and Substantiation of the Theory of Epigenesis
4. The "Theory Of Generation" of K. F. Wolff
5. Wolff's Treatise "On the Formation of the Intestine"
6. Wolff's Teratological Works
7. The Work of Wolff: "On the Special Essential Tower"
8. The Ideology of Wolff
9. The Theory of Epigenesis is in Russia at the End of the 18th Century
10. The Development of Embryology in the Epoch of the Struggle of Russian Empirical Science Against Naturphilosophie
11. Louis Tredern - The Forgotten Embryologist of the Beginning of the Nineteenth Century
12. The Study of the Embryonic Membranes of Mammals - The Investigations of Ludwig Heinrich Bojanus
13. The Discovery of Embryonic Layers - The Dissertation of Kh. I. Pander
14. Outline of the Life and Scientific Activities of Karl Maksimovich Baer
15. Baer's Treatise De Ovi Mammalium Et Hominis Genesi
16. Appearance and Significance of Baer's Main Work Ober Entw I Cklungsgesch I Chte Der Thiere
17. First Part of Uber Entw I Cklungsgesch I Chte - Development Of The Chicken in the Egg
    1. First Period of Chick Development
    2. The Second Period of Chick Development
    3. The Third Period of Chick Development
18. Second Part Of Uber Entwicklungsgeschichte - Scholia and Corollaries to the History of Chicken Development in the Egg
19. Theoretical Introduction to the Second Volume of Uber Entwicklungsgeschichte
20. Third Part of Uber Entw I C Klungsgesch I Chte - Development of the Bird Egg and Embryo
21. Third Part of Flber Entwi Cklungsgesch I Chte Continued - Development of Reptiles, Mammals, and Animals Deprived of Amnion and Yolk Sac
22. Fourth Part of Uber Entwicklungsgeschichte - Studies on the Development of Man
23. Baer's Teratological Works and his Embryological Reports, Related to the Period of his Work in Petersburg
24. On the Question of Baer's Theoretical Views
25. Investigations on Invertebrate Embryology - Work of A. Grube, A. D. Nordmann, N. A. Warnek, and A. Krohn

Comments

Illustrations To Blyakher, History Of Embryology In Russia

General

When Dr. Robert Multhauf asked me if I would consider editing this translation of Blyakher's volume, he warned that this was part of what seemed to him a most unusual scholarly project. Thanks to a somewhat mysterious and complicated government exchange program, the Smithsonian Institution and the National Science Foundation had been charged with overseeing the translation into English of several foreign language texts in the history of science. Upon the recommendation of experts, the volumes chosen included two by L. Blyakher, a Russian biologist. In particular, these Russian volumes, including THE HISTORY OF THE INHERITANCE OF ACQUIRED CHARACTERISTICS, edited by Frederick Churchill, and this one, were thought to present a valuable exposure to a Russian point of view in the history of science and to detail important episodes of Russian scientific history. Therefore, the translation began.

Following someone's recommendation, this particular volume went to Egypt to be translated by an anonymous translator. I admire the translator's patience in working through the detailed embryological descriptions. Unfortunately, however, the style of the English translation was infelicitous at best, and the translator evidently had trouble with proper names, German references, and embryological terms. My task, then, became to turn the prose into an acceptable style, to correct the names and terms to conform with standard English usage, and to check the references.

The fact that I do not read Russian, except for wordby-word translation with a dictionary, could have posed a fatal problem. But fortunately, the Dickinson College Library and work study office generously donated the services of work study student Lauri Wiener, who reads Russian and possesses the requisite active curiosity and healthy sense of humor. Together, Lauri and I checked the questionable phrases as well as a random sample of other passages to determine the accuracy of the translation. Except for some of the discussion

of German philosophy and a few embiyological descriptions, the translation appeared to us to be accurate. The fact that Blyakher's style is straightforward and essentially descriptive undoubtedly helped, since the translator could thus provide a rather literal translation without losing the content or warping the style significantly. The fact that many of the embryological terms had simply been transliterated from Latin or German into Russian and then back in accordance with standard international scientific terminology to make this translation, meant that the terms usually remained recognizable. Thus, although I make no pretense of certifying the precision of every detail of this translation, to my knowledge it is reasonably accurate at all points and represents Blyakher's content and style fairly closely. I very much appreciate Lauri Wiener's help in verifying and improving the translation.

Identifying some of the intended proper names and dates required a bit of detective work. Double transliteration or translation into Russian and then into English created much more trouble with some of the names than did translation of embryological terms. Names such as Isidore Geoffroy Saint-Hilaire or Cuvier produced mysterious and occasionally hilarious results, as the former became Izedor Zhefwar Tzent IJer, and the latter Kyuve. Joseph Needham became Nidzhem, Xeeuwenhoek became Lev'nhk, and so on. As might be expected, the more obscure names created the greatest difficulties, but with the help of the extraordinarily helpful and competent Dickinson College Interlibrary Loan staff, I managed to track down all but a couple of minor Russian figures to check spellings and dates. In questionable cases, I have used spellings from the Library of Congress National Union Catalog. And some names are left in Russian style, such as Karl Maksimovitch Baer (alias Karl Ernst von Baer, of course) to reflect the importance of Blyakher's claim that these men are essentially Russians. In this case, Karl Maksimovitch Baer is closer to the man's given name when he was born in Estonia.

References to published and unpublished materials provided even more trouble in some cases, though here, too, I was able to check and correct all except a few Russian references. A project of this type and magnitude naturally encourages some errors to creep in, so I expect that there

may be some imperfections in citations. Nonetheless, with the exception of some of the Russian articles, I have been able to verify dates, page numbers, and other significant reference data. Readers with access to a superior library should be able to locate most of the material Blyakher cites, though some of the unpublished Russian materials may well prove inaccessible as they did to me.

My other task in editing this volume lay in making the descriptive chapters on von Baer's UBER ENTWICKELUNGSGESCHICHTE useful, since Blyakher 's page number references to the Russian translation of von Baer's work would obviously not be particularly relevant for most readers of this English translation. Therefore, for the passages Blyakher quotes or cites, I identified page numbers of the German original edition, which has been reprinted recently. And where necessary I checked, corrected, and added the section references to UBER ENTWICKELUNGSGESCHICHTE. The references are thus: (volume, section, German page number) or (volume, section, Russian page number (German page number)). In addition, I corrected translation of the quotations where necessary to accord with more common English versions .

For other references to or quotations from German or English works, I made necessary corrections and substituted standard English versions where available since some passages had been distorted in the double translation.

At this point, the first round of editing was complete. Here Rosemary Regan enters the story. Ms. Regan, a marvelously competent and intelligent assistant to Dr. Multhauf, helped with typing some of the longer and messier chapters; she corrected errors in the entire draft, and she used her knowledge of editing and the history of science to polish details of style and terminology. I thank Rosemary for her considerable help and both Rosemary and Robert Multhauf for their continued encouragement and good humor.

With these acknowledgements and with the above caveats, I feel assured that this descriptive volume should be accurate and usable. Editing this has proven to be an unusual project, as Dr. Multhauf warned, but I feel, as he has felt, that the translated and edited volume can prove useful, as indicated in more detail below.

Outline of Blyakher's Work

In fact, this book represents only half of Blyakher's HISTORY OF EMBRYOLOGY IN RUSSIA, covering only the mid-eighteenth to the mid-nineteenth century. A brief discussion of the second volume, covering the mid-nineteenth to the mid-twentieth century, appears in a review by Charles Bodemer in ISIS. While that second volume describes material less well-known to western historians of science and while it might therefore seem more valuable, this volume is intriguing in part precisely because it deals with apparently familiar figures and works from a different perspective which is distinctly, though on the whole not zealously, patriotically Russian. Blyakher claims that those recognized great embryologists, Kaspar Friedrich Wolff, Khristian Pander, and Karl Maksimovich Baer - heretofore considered German embryologists - were in fact distinctly Russian, and that their Russian connections define their scientific characters and help explain their successes in important ways. This Russian viewpoint is the first of the book's two major offerings.

The second lies in the description and catalog of essentially inaccessible works and the compiling of several descriptions into a single narrative index of sorts. Blyakher discusses works of major embryologists which can be located only with difficulty. For example, even though they appeared in German (which can be read by more English speakers than Russian can), many of the papers cited appeared in some of the little-circulated publications of the St. Petersburg Academy of Science. Thus, Blyakher provides new descriptions which he combines with discussion of other both major wellknown and relatively rare sources. Since many of these sources are little known, little circulated, inaccessible, or difficult to read because of the archaic scientific detail or descriptive style, Blyakher has performed a valuable service by describing them.

I will outline the chapters briefly as a guide to Blyakher's work, since this is a descriptive study which could use some index, and its indices have not been translated into English for logistical reasons.

In the INTRODUCTION, Blyakher explains that he will give "a detailed account of the history of Russian embryological investigations" to provide "exhaustive evidence (for) the frequently repeated claim that Russia is the fatherland of embryology as a science, that it developed from Russian soil and became one of the most important foundations of the evolutionary and historical view of the organic world." Embryology - meaning Russian embryology, of course - fell into three distinct periods, according to Blyakher: that of establishing epigenesis and making embryology possible as a science (Wolff) , that of discovering the embryonic layers and establishing the prerequisites for comparative embryological development (Pander and Baer) , and that of evolutionary embryological development (Alexander Kovalevsky and I.I. Mechnikov) . The first two periods form the focus of this volume, while the third is subject of his second volume. The following chapters amass "evidence" for his claim for Russian fatherhood primarily by describing the many accomplishments of native (and adopted) Russians and by showing how these actually were in some essential way Russian accomplishments.

CHAPTER 1 considers the early period, beginning with the late seventeenth and the early eighteenth century, the time of Peter I's reorganization in Russia. Peter wanted to encourage native-born and trained scientists, Blyakher tells us, and so the ruler established a significant teratological and embryological collection in the Kunstkamera to support native medical studies. Peter I initiated Russian interest in embryology, according to the author. And Mikhail Lomonosov stimulated serious embryological studies, drawing on those teratological and embryological collections. Lomonosov, like Wolff and other followers, began the modern era of experimentation, materialism, empiricism, and historical explanation, Blyakher asserts, without fully explaining what he means by each of those recurring terms. Despite his infrequent lapses into enthusiastic excesses, Blyakher convincingly establishes that there was early embryological interest in Russia, which has not been widely studied, and that historians of science should therefore explore the subject more seriously.

CHAPTER 2 discusses the preformation and new formation (alias epigenesis) exchanges. This chapter offers few new insights into these debates, but the reader should recall that Blyakher was writing in the early 1950 ! s and that his Russian audience was likely unfamiliar (or only recently familiar) with material which a western audience might find much more familiar. Blyakher' s listing of partisans on either side and his discussion of the issues here and in later chapters are essentially clear and potentially useful even if not profound.

CHAPTER 3 introduces that great adopted Russian, Kaspar Friedrich Wolff, who then provides the subject of Chapters 5-8 as well. Wolff deserves more credit than he has received (by 1955, remember), Blyakher asserts; everyone from Russian historians to German historians to Wolff's contemporaries have reportedly been consistent in their underestimation of Wolff's significance. Here, Blyakher becomes a bit zealous in his efforts to make Russian everyone and everything which seems good or important. He faults the Russian historian and biographer Boris Evgen'evic Raikov, for example, for suggesting that Wolff felt ideologically isolated after his move to Russia in 1767. Not the case, Blyakher insists. ". . .in Germany Wolff was not evaluated as a first class investigator and advanced thinker. This forced him to move to Russia, and therefore Germany does not have the right to claim Wolff's glory."

While Blyakher 's claim is silly as stated and while it might seem exaggerated and annoying to the modern historian of science, it may also reveal valuable insight. It would be well for historians of biology to recall that Wolff was little known in Germany; that he did move from Germany to Russia in 1767, albeit after much of his major embryological work had been completed and published; that his biographers have found the reasons for his move unclear; but that St. Petersburg did offer important collections of embryological and teratological specimens and that Wolff seems to have used them to advantage. Thus, perhaps St. Petersburg did offer an especially congenial environment for an embryologist who was an epigenesist, and perhaps the reasons should be better examined.

CHAPTER 4 provides a useful outline of Wolff's dissertation - both the original Latin of 1759 and the German, more "popular" version of 1764. The Latin criticized earlier epigenetic suggestions and reflected a great deal of respect for Haller, but Blyakher claims that Wolff appealed to Haller only because he sought the latter 's support and that Wolff consistently rejected any tendency toward Haller's preformationist views. In the German, Wolff provided an epigenetic discussion of development and expressed opposition to rigorously mechanical understandings of vital phenomena. Blyakher' s description of Wolff's work is valuable, but the reader should be aware that Blyakher has probably had to strain the data here more than elsewhere to support his thesis about Russian priorities in embryology and his view that Wolff was one of the Russian "good guys" on the progressive path to modern scientific embryology. Again, the reader should recall that this was published in 1955, just shortly after other Russian publications of histories of embryology and translated embryological works.

CHAPTER 5 remains somewhat more descriptive, providing a valuable discussion of Wolff's relatively rarely read ON THE FORMATION OF THE INTESTINE. Here begins Wolff's articulated disagreements with Haller over whether development occurs gradually and epigenetically or by unfolding of preformed material. "I consider it proven that the intestine is doubtlessly thus formed (by rolling of material) and did not exist previously in an invisible form, ready to appear at the appropriate moment, "wrote Wolff in opposition to Haller. Just because he could not see the parts early on does not mean that they could not exist already, Wolff realized, but he believed that in fact the parts are only formed as the result of a gradual process. Unfortunately, Wolff's work was little known, even after a translation into German appeared. Only much later was Wolff appreciated, according to Blyakher, and it took figures such as von Baer, the American biologist William Morton Wheeler, and the embryologist-historian of science Joseph Needham to evaluate properly Wolff's "fatal blow for preformation."

CHAPTER 6 considers Wolff's teratological work, performed after his move to Russia and based on the St. Petersburg collections in the Kunstkamera. These studies, published in Latin, have remained essentially unknown until recently. After arguing that God would not have created monsters, Wolff maintained that abnormalities must occur by epigenesis rather than preformation. Blyakher asserts that Wolff's discussion of God reflected his desire to "eliminate God from nature" and that any impression otherwise stems from Wolff's necessary conformity to prevailing popular opinion. But the reader should consider this claim sceptically, a warning reinforced by awareness of Blyakher 's efforts through the last few pages of the chapter to make Wolff a predecessor of modern embryology.

CHAPTER 7 presents Wolff's "essential power" as discussed in his commentary for the 1782 St. Petersburg Academy of Science prize competition for understanding nutritional power. In a paper of his own, Wolff responded to papers by Blumenbach and Born by discussing attractive and repulsive forces and the importance of forces as well as structure for organic animal development.

CHAPTER 8 addresses evaluation of Wolff's work by Kirchhoff (Wolff brought development from mystery to a science by establishing that organic life follows laws) and Raikov (Wolff was a materialist and denied the existence of Stahl's mystical "soul," an idealist but not a vitalist, stressing the primacy of material over soul) . Interestingly, given his retrospective tendencies elsewhere, Blyakher believes that Raikov distorts the proper historical perspective, and he sees Wolff as fluctuating between materialism and idealism. Consistently, Blyakher tries to show how major figures were predecessors of modern science even though they were sidetracked by errors of their day. Thus he is Whiggish in his history, but he is not completely ahistorical. It is not Wolff's fault that he could not do more, Blyakher apologizes; the backward times slowed Wolff's progress in Blyakher 's assessment. Thus, like earlier chapters, this chapter begins with useful description and references to relatively littleknown material and ends with a claim for Russian priority.

CHAPTER 9 argues that Wolff was essentially ignored but that Russian embryologists nonetheless began to accept epigenesis by the late eighteenth century. Blyakher discusses such figures as Johannes Beseke, Matvei Pekken, Nestor Maksimovich-Ambodik, and Aleksandr Radishchev, providing a valuable, though brief, introduction to each of these scientists.

CHAPTER 10 is perhaps the most significant in introducing a cast unfamiliar characters and unfamiliar material, and in providing original theoretical discussion. After establishing what Naturphilosophie means to him, Blyakher assesses the impact of German Naturphilosophie on Russian science; he concludes that Russians were generally not receptive to Schel ling's philosophy or to idealistic Naturphilosophie in general, even though some embryologists such as Danil Vallanski, Michael Pavlov, and others endorsed seemingly idealistic views. The Russian intelligentsia recognized the unreality of Naturphilosophie and the importance of materialism, Blyakher argues, and thus they moved toward a progressive empirical philosophy. Despite apparent flirtations with Naturphilosophie, therefore (as for von Baer) , Blyakher concludes that "the successful aspects of embryology in Russia were thus not connected with Naturphilosophie." Although once again consistently retrospective and apologetic for the seemingly imperfect progress of Russian science, Blyakher has in this chapter addressed the suggestion by others that Naturphilosophie may have directed Russian science and argues that it may have been seriously considered but then rejected or refined in "successful" Russian science. His discussion of those who did accept some form of idealistic philosophy is useful, as is his interpretative assessment of its limits.

CHAPTERS 11 AND 12 sketch, respectively, the contributions of transition figures Louis Tredern and Ludwig Bojanus. Tredern admittedly "was not a Russian, was not born in Russia, and lived there only six years." Yet he was an honorary Russian in Blyakher' s view. Tredern did produce an influential dissertation, reportedly inspired by the Russian Wolff and by Tredern 's visit to St. Petersburg; there he outlined the preliminary story of the avian egg and its hatching and early development. Bojanus introduced study of the embryonic layers in mammals, which influenced Pander and von Baer, according to Blyakher.

CHAPTER 13 discusses Khristian Pander, von Baer's fellow student at Wurzburg studying under Dollinger. Dollinger and von Baer convinced Pander to apply his apparently significant financial resources to procure the necessary large number of eggs in order to trace details of chick development during the first five days of life. Pander's work, despite criticism by Lorenz Oken which Blyakher discusses in detail, provided a starting point for future study in epigenetic developmental biology, and especially notably, it served as a foundation for von Baer's work. At one point, Blyakher almost perversely manages to make Pander's weaknesses sound like strengths. He says that Pander's errors were valuable and that they were important in part because they later "allowed Baer to give the true interpretation." As before, Blyakher 's interpretation remains retrospective and frustrating at times, but his data are useful for an introduction to this material.

CHAPTER 14 THROUGH 24 deal with Karl Ernst von Baer, here Karl Maksimovich Baer. 14 provides biographical information and outlines his professional career. 15 presents Baer's discovery of the mammalian ovum and reveals concern both with establishing Baer's priority and with opposition to Baer's work. CHAPTERS 16 THROUGH 2 2 describe Baer's opus, UBER ENTWICKELUNGSGESCHICHTE. Originally published in Germany (volume 1 1828, volume 2 1837, volume 2 part 2 1888), Baer's work appeared in Russian translation only in 1950 and 1953, which may have provided one stimulus to Blyakher to publish his historical study. Blyakher evidently relied on the Russian translation, so I have had to provide references to the German original (as mentioned above). Few people have read through Baer's long and detailed study completely, so Blyakher 's discussion of all five scholia and corollaries and of the rest of the work, of which many are aware but which few read, will prove useful.

Most important, though, is the discussion of Baer's volume 2, and especially in CHAPTER 2 2 of the fourth part which forms the second part of volume 2. This section was published not by Baer himself but by Ludwig Stieda, after Baer's death. Baer had not completed the work, and Stieda discovered the manuscript while working through Baer's materials in order to produce a biography. Baer had begun his study of human development, discussed in this part four, in Konigsberg in 1834, but his move to St. Petersburg that year disrupted his work and he never completed his examination of human normal and abnormal development.

Human development also forms the subject of part of CHAPTER 23, which deals with Baer's teratological work in St. Petersburg. Here Blyakher addresses Baer's complaints about "lack of consideration or unfair attacks, with which his remarkable discoveries were met in Prussia." The Russians were more sympathetic, of course, according to Blyakher. In part because the Germans did not fully acknowledge the importance of his work, Blyakher establishes convincingly, Baer returned to Russia and gave up his systematic embryological studies, turning instead to anthropology and other scientific and family ventures.

The few studies of fertilization and embryological development which Baer did perform after his move, Blyakher discusses, including several papers detailing what is essentially meiosis and mitosis, according to Blyakher. If fertilization and cell-division initiate development, then there could be no pre-existence of individuals; the unfertilized ovum must contain latent but not pre-formed life, Baer had concluded in a paper of 1847. Some of Baer's teratological and fertilization studies reveal that Baer accepted a limited version of evolution - an evolution of the individual within his system of types. Blyakher neatly illustrates the transition between his second and third historical periods of embryology with the example of St. Petersburg Academy of Science's establishment of a prize for Biological Science in 1864. Kovalevsky and Mechnikov won that prize, thus bridging the move from Baer's older epigenetic work to the new evolutionary embryological science.

CHAPTER 2 4 considers Baer's theoretical views, including a very brief look at Baer's version of the history of science. This chapter offers intriguing suggestions, but most are incompletely developed and hence do not significantly extend our understanding of Baer. As with the rest of the book, the chief value of these lengthy chapters on Baer lies in the potential of their suggestions, in the descriptions of more well-known sources and of unfamiliar material alike against a background of other familiar works. The references provided certainly suggest that Baer is as yet poorly understood, despite the several biographical sketches, and that historians of science would do well to explore his complex Russian connections - both before his move to and after his return from Germany.

CHAPTER 2 5 serves as a transition to the third stage of world and hence Russian embryology (featured in Blyakher's second volume) . It considers figures after Baer but before Mechnikov and Kovalevsky. The focus is on Grube, Nordmann, Warnek, and Krohn in particular. These men made way for Kovalevsky and Mechnikov, according to Blyakher, and these latter men effected the revolution from comparative-descriptive to comparative-evolutionary embryological science.

NOTES - These notes have not been translated, obviously. Some offer biographical information, others provide references to additional scientific and other works, while still others elaborate on the text. These notes are cited in the text by the numbers enclosed in square brackets: (#) .

The above brief outline sketches Blyakher's volume. Throughout, the work remains descriptive. Each chapter thus provides details of the works and people it considers. Some of these descriptions are so extremely thorough as almost to reproduce the original sources being considered, while others provide essentially an index or overview of their subjects. To my knowledge, the descriptions seem consistently reliable and useful.

Value of the Work

As suggested above, Blyakher's work contributes both useful description of little-read source materials and a particularly Russian perspective. The latter, which clearly directs what interpretation Blyakher does offer, only occasionally intrudes on the narrative. As noted earlier, Blyakher does at rare times become fervent in his attempts to establish that "Russia is the fatherland of embryology as a science." Yet he would appear to have considerable evidence that his claim should at least be taken seriously. Western scholars often tend to dismiss Soviet scholarship and its fiercely patriotic perversions. But Blyakher, despite his effectively cold war context, remains relatively restrained and reasonable.

The author's concern with establishing scientific priorities, with establishing who first discovered such-andsuch, seems equally open to objection from the perspective of current history of science. Yet this orientation clearly does not result strictly from Blyakher ' s Russian point of view; most historians of science in the 1950' s sought to establish priorities and to document high points of scientific "progress."

In sum, then, Blyakher does provide a very useful descriptive guide to major works in the history of embryology, many of which happen to be Russian in some sense. His interpretative discussion, which seeks to establish that the Russian connection in important embryological work was not merely coincidental needs to be questioned, dissected, and then explored further to discover just what the essential Russian influences were. We should thank Blyakher for his suggestions and use his volume as a guide for that further exploration.

Because the materials are so widely known, I have decided not to provide a full bibliography of works relevant to the subjects Blyakher discusses. See the DICTIONARY OF SCIENTIFIC BIOGRAPHY entries for the key figures and standard sources in the history of developmental biology for additional references and for discussion of similar materials from various non-Russian perspectives.

Jane Maienschein

July 1981 Arizona State University

Preface

Embryology occupies a notable position among the biological disciplines of Russian science, as noted by K. A. Timiriazev. 1 Separate stages of the history of Russian embryology are presented in journal articles, collected biographical essays, and commentaries which have accompanied the recently published works of the Russian scientists K. F. Wolff, K. M. Baer, A. 0. Kovalevsky, and I. I. Mechnikov There is no systematic treatise of the history of embryology, either here or abroad. 2 Joseph Needham's HISTORY OF EMBRYOLOGY, which was translated in 1947 into Russian, 3 cannot satisfy any exacting reader. (1)4 For exhaustive evidence of the frequently repeated claim that Russia is the fatherland of embryology as a science, that it developed from Russian soil and became one of the most important foundations of the evolutionary and historical view in the organic world, therefore, it is necessary to give a detailed account of the history of Russian embryological investigations K(liment) A(rkadevich) Timiriazev, "Istoricheskii metod v biologii" (Historical methods in biology) .... SOCH., V.VI.M., Selkhozgiz (1939), p. 32.

This confirmation is correct now only in relation to the history of embryology of animals . After the manuscript of this present book was given to the press , there appeared P(avel) A(leksandrovich) Baranov's monograph, ISTORIYA EMBRIOLOGII RASTENII V SVYAZI S RAZVITIEM PREDSTAVLENII ZAROZHDENII 0RGANIZM0V (History of plant embryology in connection with developmental ideas on the generation of organisms) (Moscow: Akademii Nauk, 1955, 439 pp.) . In the first part of this book its author presented the prehistory of the embryology of plants , to the nineteenth century, against the background of development of general ideas on the generation of organisms, both plant and animal (p. 8) J. Needham, HISTORY OF EMBRYOLOGY, translated from the English by A. V. Yudinaya, preface by V. P. Karpov (IL, 1947) , 342 pp.

Numbers in square brackets are related to the comments at the end of the book .

The first observations of embryonic development date back 2,500 years; however, the onset and development of embryology as a science is connected with the general progress of the natural sciences in the eighteenth and nineteenth centuries. There are three main stages in the history of embryology. The period of the substantiation of the theory of epigenesis, making possible the existence of embryology, is connected with the Russian academician K. F. Wolff. The period of the discovery of the embryonic layers, when the prerequisites for comparative embryology appeared, is the period of activity of the Russian academicians Kh. I. Pander and K. M. Baer. Finally, the period of the creative development of embryological problems in the light of Darwin's work is inseparably united with the Russian investigators A. 0. Kovalevsky and I. I. Mechnikov and the brilliant zoologists who followed their footsteps.

The present book reviews the first two periods of the history of embryology, including the epoch directly preceding the scientific activity of A. 0. Kovalevsky and I. I. Mechnikov. The history of Russian embryological investigations, from the beginning of comparative embryology to the present time, is embodied in the contents of the books discussed here. One is dedicated to the history of embryology of invertebrates and another book elucidates the history of the embryology of vertebrates.

At the time of writing the present book, no work of Wolff or Baer had been published in Russian except for the incomplete and inaccurate translation of the second part of the first volume of Baer's UBER ENTWICKLUNGSGESCHICHTE .5 In 1950, in the academic series "Klassiki nauki," the translation of Wolff's "Theory of Generation" appeared, as did the translation of the two volumes of Baer's "History of Animal Development" in 1950 and 1953. An article by Gaissinovich 6 (in an appendix to Wolff's book) clearly presents this embryologist 's ideas against the historical background of studies of evolution. An analogous article by B. E. Raikov concluded the first volume of Baer's work. 7 The appearance of these articles has reduced the corresponding chapters of the present book, but the author considers it necessary to give a brief, thorough review of the basic works of Wolff and Baer in connection with their other embryological and teratological works.

5. K. M. Baer, IZBRANNYE RABOTY (Selected works), from the series KLASSIKI ESTESTVOZNANIYA, translated with comments and preface by Yuri A(leksandrovich) Filipchenko (Moscow: GIZ, 1924), 114 pp.

6. A. E. Gaissinovich, "K. F. Wolff and Studies on Development," in an appendix to K . F. WOLFF: THEORY OF DEVELOPMENT (Moscow: Akademii nauk, 1950), pp. 363 - 477

The works of Russian embryo logists of the eighteenth and the beginning of the nineteenth centuries — Wolff, Tredern, Pander, M. G. Pavlov, and Baer — are, in part, written in Latin and cannot be read in the original by the majority of our young contemporaries. The literary legacy of Baer is extremely vast and difficult to review.

It seemed to the author that it is important to explain not only the most important works of the Russian embryologists of the second half of the eighteenth century and the first half of the nineteenth century, but also their less important works, in order to present the contribution which Russian investigators made to world science. The activity of the Russian embryologists coincided closely with the development of world embryological science. The importance of the Russian investigations can be correctly evaluated only in comparison with the works of the foreign embryologists, which are explained by short comments in the present book. Expansion of these excursions into the history of world science did not seem possible without significantly increasing the size of the book.

In presenting the contents of the Russian embryological works, sometimes sufficiently long extracts are presented that the reader can form an impression not only about the contents, but also about the scientific literary style of the investigations discussed.**

7. B(oris) ECvgen'evich] Raikov, "On the Life and Scientific Activity of K. M. Baer," in an appendix to K . M. BAER: THE HISTORY OF ANIMAL DEVELOPMENT, Vol. I (Moscow: Akademii nauk , 1950), pp. 383 - 438.

8. All the citations printed are underlined by the authors of the discussed works permitting the reader to see exactly what the authors, themselves considered most essential in their works .

The drawings are considered to be the most important part of the morphological works. The pictures, reproducing the studied objects as they were seen either with the naked eye or with the aided eye, reveal the level of the technique and the exactness of the observations. The schematic drawings are considered the graphic expressions of the authors' theoretical opinions. Therefore the original drawings speak about the scientific priorities and facilitate the description in words of the corresponding discoveries. In reference to this, we must not forget the authors of revisions and educational textbooks; although they occasionally reprint the illustrations of the foreign authors, often they are not a bit better than the drawings of the Russian investigators published earlier. The reprinting of the original drawings of Wolff, Tredern, Boyanus, Pander, Baer, Grube, Nordman, Warnek and Krohn in the present book is to present the level of their morphological investigations, and also to defend the priority of the Russian embryologists .

The present book was finished in 1950. Its contents, and also the plan for its continuation to subsequent stages of embryology in our country, were reported in the meeting of the sector of the history of biology in the Institute of Natural Science History of the Academy of Science of USSR and in the Academic Council of this Institute.

The author is deeply grateful to T. D. Detlaf; L. D. Lioznera, S. R. Mikulinsky, S. L. Sobol and G. A. Shmidt, who listened to the reports about the contents of this book or read the manuscript and made critical comments. The author particularly thanks the collective of the library of the Moscow Society of Naturalists, who willingly helped during the search for literary sources and illustrated materials.

Chapter 23. Baer's Teratological Works and his Embryological Reports, Related to the Period of his Work in Petersburg

Baer was not a pioneer of teratological investigations in Russia. By the middle of the eighteenth century the Anatomical Museum of the Academy of Science had available a significant collection of preparations demonstrating the abnormal development of man and different animals. Before the arrival of K. F. Wolff in Russia, the materials of these collections had been little investigated, excepting the more or less accidental descriptions performed by A. Kau-Burgav. Wolff very energetically undertook the investigation and description of the abnormalities in the Academy's collection, connecting to them the material personally collected by him. However, because he was involved with vast anatomical investigations, he published only some of his observations e A great part of them were to have been included in the great work which was left unfinished due to his unexpected death, and which consequently did not appear. At the beginning of the nineteenth century the teratological collections were put in the reliable hands of Academician P. A. Zagorsky, organized, and again studied intensively. Zagorsky had time to investigate and describe only a small number of interesting teratological cases.

Eventually Baer settled in Petersburg. Despite his varied activities connected with investigations in different spheres, and with administrative, educational, and experimental work, he found time for teratological investigations. At this time he was not a beginner in this sphere. He was still a professor in Konigsberg when he published some small articles, from which information about deformed swine embryos has been mentioned.

In 1827 Baer published an article on a double chicken embryo at the beginning of the third day of incubation. 1 The purpose of this work was to solve the disputed question of the origin of double monsters. "I never could bring myself to accept the idea," Baer wrote, "that double monsters arise from the union of two individuals, although previously many physiologists insisted on this opinion. It seems to me that here one difficulty has replaced another" (p. 576) . The arguments proposed by Baer against the theory of union were very close to those used by Wolff in his "Description of Two-Headed Calf, accompanied by general illustrations on the origin of monsters." 2 In order for two embryos to unite in an earlier stage of development, it would be necessary for them to be completely movable and for there to be pressure upon them from two sides, pressing them together. But the main difficulty lay in the fact that it is impossible to imagine how the corresponding parts of the two individuals meet and why the union takes place without disturbing the topography of the parts. More naturally, Baer supposed this case to represent the splitting of a formerly unified rudiment. This explanation did not eliminate all the difficulties; it was suitable for the interpretation of lateral splitting, but left unexplained the cases of divergence of surfaces and union of twins by the ventral sides.

Baer thought that the solution to this interesting question could be achieved only through the study of the early stages of development of double monsters. He described one of these cases, in a developing chick at the beginning of the third day of incubation. The transparent zone CAREA PELLUDICA) had a cruciform shape with two long and two short ends; the embryos were situated in the long ends, the posterior ends of which moved apart and the anterior united in a general mass. Both the embryos were equally developed. The spinal plates, containing the foundation of the vertebrae (Pander's PLICAE PRIMITIVAE) were closed, enveloping the spinal cord; the abdominal plates (Wolff's LAMINAE ABDOMINALES) were situated nearly horizontally, i.e. the body of the embryo was still opened from below. The spinal plates passed without discontinuity into the common head, and the spinal cord into the common brain.

1. Baer, "Uber einen Doppel-Embryo vom Huhne aus dem Anfange des dritten Tages der Bebrutung," ARCH. ANAT . PHYSIOL. (1827) , pp. 576-586.

2. K. F. Wolff, "Descriptio vituli bicipitis . . . ," NOVI COMMENT. ACAD. SCIENT., PETRPOL.,32 (1773),

pp. 504-573 (see Chapter 5) . Baer did not refer to this work by Wolff. Baer's exceptional honesty, which appears in all his works, suggests that Wolff's paper on the double-headed calf was for some reason unknown to Baer.

Baer thought it improbable that these partners were at first divided, and then united. In the period up to the third day of incubation, i.e. when the beginning of the process of union could be expected, the embryos cannot move nearer to each other because they are still situated in the convexity of the blastoderm. If it is assumed that the first foundation of the double embryo was single, that the foundation of the head was formed not at its end but in its center, then the formation of the double embryo becomes understandable. The dorsal region of the cephalic end of the embryo grows more quickly than its other parts; therefore in the single embryo the head is curved downwards, and in the double embryo the frontal parts moved away from each other. The cruciform embryonic structures meant that the basis of double-embryo formation occurred in the ovum very early.

To the question of the origin of double monsters Baer returned in two works published in Petersburg ten years later, The first article^ was very brief and was, in fact, a preliminary to the second, which was a vast work. 4

3. Baer, "Uber doppelleibige Missgeburten," MEM. ACAD. SCIENCES ST.-PETERSB. , VI Ser., v. 3, book 2BULL. SCIENT.,No. 2 (1835), pp. I-II.

4. Baer, "Uber doppelleibige Missgeburten oder organische Verdoppelungen in Wirvelthiern," MEM. ACAD. SCIENCES ST. PETERSB.,TV Ser. Sc. nat., v. 4, Zool. et physiol. (1845) , pp. 79-194.

Baer first referred to his findings in 1827 on the double chicken embryo, where only its description had been carried out. He again raised the question of how these monsters were formed, disagreement about which had long existed in the literature on this subject. Haller and Meckel in their own day stated their opinion that double monsters develop by way of union. Burdach later subscribed to this interpretation. Isidore Geoffroy Saint-Hilaire was a more active supporter of the theory of union. Baer decisively raised an objection to this point of view. So he was astonished to find that Barkov, in his thorough work, "Double Deformities among Animals," claimed that Baer's description of the embryo "proved directly the union of separate parts of the accreted embryo." How could it happen, Baer wrote, that, "considering myself a decisive opponent of accretion, I have apparently recognized the accretion of parts of different embryos?" (p. 81) . From the moment of the appearance of Barkov' s work, Baer collected additional data on double monsters, on the basis of which he reconfirmed the accuracy of his previous opinion.

Speaking of investigations of monsters generally, Baer stated that their development must be studied as exactly as the course of normal development. The achievements of embryology, making the controversy of spermatists and ovists meaningless, was a consequence of that. From elucidation of the primary conditions of the processes of reproduction and development we arrived at the fundamental study of the most formative processes.

Before turning to the description of many cases of double monsters, Baer outlined his order of presentation. In the beginning he investigated what was formed; later, by comparison with other cases and with normal development, he elucidated the question of how these monsters could be formed. Concerning why these double monsters originate, only suppositions are stated.

DOUBLE EMBRYOS OF FISH IN VERY EARLY STAGES OF DEVELPMENT. Baer began with the description of two double monsters in perch which he found in 1835 in some eggs obtained from the Neva two days before the investigation. One embryo was double-heated. In the other the division was found in the trunk region. The division of the cephalic end of the first embryo was incomplete, since there were two mouths and four eyes but only two ears (Figure 34, A) . In the second embryo the posterior part of the body and tail was single and all the anteriorly situated parts were double. Both these cases, in Baer's opinion, totally excluded the possibility of regarding them as a result of the union of two individuals: from the moment of the appearance of the embryo not more than one day elapsed; thus during this short period the remaining undoubled parts could not have disappeared. In addition, the embryos were situated close to the yolk. They could not have been any closer in order to unite With each other. In an embryo with a partially doubled head, it can be assumed that the splitting occurred in a very late stage. In the second embryo the bodies were situated at an angle of 120°, indicating that the first foundation of the embryo, namely the primary streak, was divided from the front. The unusual width of the ovum supported this observation. A double embryo appeared after the division of the primary single rudiment. In connection with the description of these cases of double monsters in perch, Baer referred to examples of double embryos in fish described in the literature, beginning with Aldrovandi's MONSTRUORUM HISTORIA (1642) and ending with Heusner's "Double Monsters in Perch and Other Fishes". ^

DOUBLE CHICK EMBRYO AT THE BEGINNING OF THE THIRD DAY. In this section Baer gave a more detailed description of a divided chick embryo, the investigation of which was illustrated in 1827 (Figure 34, B) . Here Baer turned his attention to the reciprocal situation of the heads of the double embryo, excluding, in his view, the possibility of the union of two formerly divided embryos. He considered especially conclusive the reasons relating to the situation of dorsal and mainly ventral plates of both partners. "The ventral plate of one of them passed into the convexity of the blastoderm without interruption and without evidence of union in the ventral plate of the other. More exactly, one and the same continuous surface formed the future left ventral wall of one, and the future right ventral wall of the other partner .... If union had occurred during the first day of incubation, then the ventral walls could not unite, since they did not yet exist; hence they were isolated from the blastoderm only in the second day" (p. 110).

5. Heusner, "Descriptio monstrorum avium, araphibiorum, iscium." Diss, inaug. Berol. (1824) (cited by Baer) .

Later Baer described some cases of monsters in man. First he described twins which were joined at the forehead. In his opinion, this case was similar to the described in 1501 by Sebastian Minister. Baer cited an early description and illustration of a human double monster, according to data provided by Schmidt, published in the journal ISIS in 1825. He followed with general descriptions and drawings of "parasitic formations," as Burdach called them — i.e. additional parts attached to completely developed individuals, which were without an umbilicus and were nourished through its vessels. Baer referred to a similar case which he had observed in Konigsberg. The case involved a living baby whose incomplete individual hands and legs were attached to its chest but who lacked a head and a large part of the trunk .

Referring to analogous examples from other authors, Baer mentioned a case been earlier studied by Zagorsky.6 He noted that that famous Russian anatomists' s description, with the exception of some details, was completely correct. In this parasitic formation, as in other analogous specimens from the Academy's collection, the supply of blood occurred from arteria mammaria of the original individual. In addition to these cases,' Baer saw examples of formations of additional extremities, always, however, connected with the other additional organs. This category, called "parasitic formations," also included those cases where two additional legs are present with an atrophied foetus, attached to»the pubic region and situated in the normal legs (Figure 34, D) . The genital organs and the internal organs of the pelvic cavity were also doubled. In a similar monster there was an additional leg without a mate; in the groin region of the extra leg were discovered an additional ovary and three elevations which undoubtedly were nipples. In this connection Baer thought the common phenomenon of supernumerary nipples in humans as being possibly inherited. He cited a case, described by Rober, in which a woman who had additional mammae on the right side of the thoracic cavity gave birth to a daughter with an additional mammae on the thigh. These additional mammae subsequently secreted so much milk that the woman could nurse, in addition to her own children, three additional babies for six years.

6. P. Zagorsky, "Foetus humani monstrosi, alii bene formato foetui adnati descriptio," MEM. ACAD. SCIENCES ST. PETERSB., VI s£r. Sc. math, et phys., v. 2, book 2 (1833) , pp. 187-194.

Besides the cases mentioned of parasitic formations in human beings, Baer described an analogous case in a live adult cow? (Figure 34, C) . In the middle of its neck there was an appendage resembling in form the scaled-down underdeveloped posterior parts with two deformed legs and a tail. The immediate investigation showed, however, that the additional legs were not posterior but anterior, and the tail-shaped structure contained a rudiment of skeletal parts of the branchial girdle. Baer investigated in detail the nerves of the parasitic formation from the cervical part of the spinal cord.

This thorough teratological work of Baer's remained incomplete information intended for the second part was never published. Probably Baer intended to include at the end of the work some theoretical consideration of the origin of double monsters. However, that which did appear in his published work is enough to suggest his point of view on this subject. As previously observed, Baer decisively rejected the idea that double monsters result from the union of formerly separated individuals. He concluded that double monsters can be formed only from the fission of the formerly single embryo. Baer supposed that the separation would be more pronounced the earlier the fission took place. The cases of "parasitic formation" Baer was inclined to interpret, apparently, from this point of view. It must be noted that Baer's principle of explanation of double monsters was subsequently completely confirmed, especially when it was found that this kind of formation could be obtained experimentally by pretwisting the ova, turning the vegetative pole upwards, effecting temperature changes, and so on.

7. Information about this case was obtained by Velyaminov from the Caucasus, which Baer published earlier under the title, "Bericht uber eine ausgewachsene Missgeburt," BULL. SCIENT., ACAD. IMP. SCIENCES DE ST. PETERSB (1836), No. 1, p. 128.

In subsequent years Baer from time to time returned to teratological questions, describing interesting cases he discovered. The following cases present information of this nature :

1. "A new case of twins joined at the forehead, and comparison of it with analogous cases. "8 This concerned accreted twins, aged about eight months of uterine life, prepared for the Academy's collection. Both the foeti are female, well developed, joined to each other obliquely. Baer noted that similar kinds of union of accreted twins are seen more frequently in birds than in mammals and cited corresponding references.

2. "Notice sur un monstre double vivant "9 This case is that of a monster which attracted Baer's attention because the accreted double was delivered at full term and was born alive. The position of the twins was completely symmetrical, in contrast to the previous case, where they were at angles to each other ,

3. "Remarks on blind fish, an example of delay of development. "10 In these remarks Baer described a carp [Cyprinus gibelio) caught in a muddy pond in Kolomyaga. The eyes of the fish were rudimentary and sealed under the skin. In connection with this Baer posted the question, can darkness be the cause of underdevelopment of the eyes?

8. Baer, "Neuer Fall von Zwillingen, die an Stirnen verwachsen sind, mit ahnlichen Formen vergliechen. Mit einer Tafel," BULL. PHYS.-MATH. ACAD. SC. ST. PETERSB. (1845),

3, No. 8, pp. 113-128.

9. Baer, "Notice sur un monstre double vivant, compose de deux enfants f eminins , " IBID. (1856), 14, No. 3, pp. 34-37.

10. Baer. "Ein Wort liber einen blinden Fisch als Bildungs Hemmung," BULL. ACAD. SCIENCES (1862), 4, pp. 215-220.

Figure 34. Illustration from Baer, "On Double Monsters."

A — double-headed perch embryo; a — outer or upper plate of the rudiment corresponding to the abdominal wall of the embryo j b — Internal or ventral plate of the rudiment or allantoic sac. B — double-bodied embryo of a chicken in the embryonic sphere, at the beginning of the third day; ABCD — transparent embryonic sphere; E — the common head; F — approximate outlines of the heart; a — thickened place on the head between the skull and thickened edge of the abdominal plate . C — adult cow with additional growth in the left side of the neck. D — newborn baby with additional legs in the pubic region.

After Baer arrived in Petersburg he ceased his systematic study of embryology. This change in his scientific interests foreign biographers explained as due to difficulties in getting embryological material. Baer himself in his autobiography supported this version of the story of how he could not organize a supply of frogs, fish eggs, and mammalian embryos. Even N. A. Kholodknovsky, the author of an excellent biography of Baer, in spite of Academician V. F. Ovsyannikov's contrasting opinion, 11 also cited the same strange explanation of the striking fact that this great embryologist, who was making more scientific progress than all his predecessors, suddenly left this sphere of science in which he had enthusiastically worked for more than fifteen years.

The true cause of why Baer stopped his study of embryology appears in extracts of his correspondence reported by B. E. Raikov in the commentary to his translation of Baer's autobiography. 12 Raikov cited a long portion of Baer's letter of December 30, 1845 to T. L. Bischoff (published in ALLGEMEINE ZEITUNG, 1880, No. 325, appendix). In this letter Baer explained his departure from embryology as due to the lack of consideration and the unfair attacks with which his remarkable discoveries were met in Prussia. The Minister of Education, Altenstein, after the publication of DE OVI MAMMALIUM ET HOMINIS GENESI, declared that "the existence of the mammalian ovum had been known for a long time," and Plagge attempted to claim for himself the fame of the discovery of the ovum in the ovary. Other German biologists showed extreme indifference to his work, which offended Baer. Not finding sympathy in their midst and not receiving from the Prussian Ministry of Education the necessary material for continuation of embryological work, Baer, in his words, "decided to tear radically from his heart all scientific ambition." Baer spoke further about his promise to himself to cease his work on embryology and not even to read any embryological literature for nine years. This decision was taken undoubtedly because of nervous exhaustion caused by severe overwork and annoyance, and Baer himself certainly regretted it. "Generally I cannot decide," Baer wrote in the same letter, "whether I behaved correctly by making this vow, but I can confirm that I have injured myself deeply, perhaps even too deeply. Later it seemed to me that I had lost the best blood of my heart."

11. F. V. Ovsyannikov, "Brief biography of Baer read in December's general meeting of the Society of Naturalists," TR. SPB OBSHCH. ESTESTV. (1877), 8, pp. 97-107.

12. The materials stated below are cited with commentary 8 in Chapter 15 (pp. 519-523) .

Discussing the contents of this truly tragic letter, B. E. Raikov correctly concluded that "there is no basis for placing responsibility for the change in Baer's scientific studies upon conditions in Russia. Not the Russian, but the Prussian conditions of his life created in him this attitude which led him to a decision so unfortunate for science."

However, in the 1840s Baer's interest in embryology reawakened, undoubtedly in connection with his professorial activity in the Petersburg Medical -Surgical Academy, where he taught comparative anatomy and physiology, in which course embryology figured significantly (114) . In connection with teaching the science so near to his interest, Baer intended in 1843 to publish a Latin "essay on the history of development of men and other animals" (CONSPECTUS HISTORIAE EVOLUTIONIS HOMINIS ET RELIQUORUM ANIMALIUM) in twelve to fifteen papers with two tables of illustrations. In 1844 invited the conference of the Academy of Science to publish an atlas in Russian on this topic comprising forty papers and 150 drawings. A report by Baer on the plan of this publication was fully published in E. N. Pavlovskii's K. M. BAER AND THE MEDICAL -SURGICAL ACADEMY. The following parts of this document are interesting:

New investigations in 'developmental history' which have already been published are still little known in Russia .... Consequently it is reasonable now to wish for a textbook on one branch of physiology developing in recent times. This branch is riot only important for physicians, and for naturalists generally, but it also illuminates other parts of physiology and anatomy. Once I dared to hope that I possessed sufficient knowledge in this subject ....

The first priority is to become acquainted with all current results in addition to the necessary details of the experiments on which they were based ....

Further, it seems important also that the application of an explanation to congenital deformities must be not only mentioned, but also investigated in order that all educated physicians can learn how to recognize and describe similar cases for the further benefit of science. The main task must be, without any doubt, the history of the formation of the human embryo, including the deformities as well. But the first stages of this formation in man are still little noted, and that includes embryos in diseased conditions (to which all abortions are related) , without which we could not know the complete history, origin, or formation of any part if they were observed in mammals. The history of formation of mammals also cannot be understood at this stage if we do not have cases of observations on the formation of chicks. On this basis I find it necessary, before treating the history of human formation, to discuss as a preliminary the observations on other mammals and on the chicken in order to understand how the results are obtained and why and to what extent analogies can be drawn from them. It is necessary to discuss briefly the animals of other classes in relation to the history of formation, and especially to mention some general results ....

These extracts from the draft of Baer's work on the history of development of man and vertebral animals show what great educational significance Baer accorded to the field of embryology in the training of future physicians. Here also was briefly pointed out the fruitfulness of the comparative method in embryology, and also the importance of the detailed study of monstrosities, a description of which is necessary "for the future benefit of science."

The publication of Baer's projected textbook for some reason did not take place. The possibility cannot be excluded that Baer himself rejected this idea. Feeling the difficulty of the great work related to a sphere of science to which he was so close in the past, he was obliged to abandon it. Actually, it was not easy after a ten-year interval, during which Baer did not study embryology and did not follow the literature of this topic, to coordinate all that had been done by a complete galaxy of investigators — Rathke, Reichert, Kolliker, Bischoff, and others — who had followed in his footsteps, adding many new facts and raising new theoretical questions. It was also necessary to take a definite position coneming the cellular theory, which in the 1840s had spread its influence to embryology. In addition to this, and even in later years when Baer wrote his autobiography (i.e. in the 1860s), he did not consider it possible to speak decisively concerning this theory. Recognizing the importance of that wide biological generalization which the cellular theory considered, Baer could not agree with the discrete presentation of the organism which was proposed by some supporters of the cellular theory in the first period of its development, and later in the era of Virchow and Schultze.

However, Baer retained an interest in the problems of the history of animal development. In 1845-46 he made an attempt to return to research in embryology. Planning to study the embryonic development of invertebrates, Baer travelled to the Mediterranean coast and collected interesting material in Genoa, Venice, and mainly in Trieste, which consisted of fixed objects and drawings by an artist who accompanied him. In this last attempt to return to embryological investigations, misfortune pursued Baer. Part of the material was accidentally destroyed in Venice; another part of it was lost elsewhere.

But not all of the research carried out on the Mediterranean coast could be considered fruitless (115). The principal task of his trip to Genoa, Venice and Trieste, as Baer wrote in his report, 13 was the study of the possibility of artificial fertilization in different marine animals (116) .

13. "Auszug aus einem Berichte des Akademikers v. Baer aus Triest zom 1 (13) November 1845," BULL. PHYS.-MATH. ACAD. SC. ST. PETERSB. (1847), 5, No. 15, pp. 231-240.

Baer noted that since the time of Spallanzani it was known that it is easy to fertilize artificially the ova of frogs. Spallanzani (and later Rossi) inseminated a bitch by the artificial introduction of sperm. Baer's contemporaries, according to him, questioned these data, although without foundation, because Bischoff's work had made it apparent that in mammals and also in other animals, the separation of the ovum is due to its maturation and not a result of copulation.

Baer thought it evident that every mature ovum introduced into contact with sperm of the same species is fertilized and, if situated in suitable conditions, develops into an embryo. Sometimes experimental difficulties arise, which can, however, be overcome. His failures in Petersburg with artificial insemination of fish ova Baer explained by unsuitable temperature conditions.

In Genoa at the end of August 1845 Baer made the first experiments in the artificial insemination of the ova of Ascidians. "In the earliest hours," Baer wrote, "the division began, and before the day had passed larvae hatched in the form of large cercariae." The experiment of artificial insemination of mature ova of the sea urchin, carried out on the same day, was also crowned with success. Within sixteen hours freely moving embryos developed. "It was a very great success for one day," Baer stated: "a researcher rarely succeeds sufficiently to exclaim VENI, VIDI, VICI! After the first glitter, I was on top of the world" (p. 233). However, it was extremely difficult to keep the ascidian larvae alive. They died within hours after hatching; the sea urchin larvae did not live more than four days.

Gaining success in the artificial fertilization of the ova of sea urchins, Baer turned to study their development. He observed the early stages of development at first in Genoa

13. Extracts from this report were published in FRORIEP NOTITZEN (1846, No. 39, pp. 38-40) under the heading, K. E. v. Baer, "Neue Untersuchungen iiber die Entwickelung der Thiere . "

in the ova of Echinus hrevispinosus (esoulentus) 9 and then in Trieste on the smaller, more transparent ova of Echinus lividus (saxatilis) , with the first, his attention was attracted to the fact that inside the ovum, soon after fertilization but before the beginning of division, a light radiance appeared but shortly afterwards disappeared. Applying slight pressure upon the ovum, Baer could get an extended vesicle (nucleus) or two vesicles situated side by side. Noting the direction of the longitudinal axis of this extended light region, Baer observed that after the yolk (ovum) divided into two halves, the centers of these halves were situated in the same axis. From these first observations he concluded that "the processes in the internal region of the ovum precede the division of the yolk and predicate it," The study of the subsequent stages of division led Baer to the conclusion that the externally observable phenomenon of division always precedes the division of the transparent nucleus present inside. The details of the ovum structure, using intravital observations with little magnification, Baer of course could not investigate, and discussions preserved the terminological confusion of that time, when the relations between the nucleus of the immature ovum (embryonic vesicle, or Purkinje's vesicle), the ovum nucleus, and its nucleolus (Wagner's spot) were still not established. 14

For the first stage of development of the immature ovum, Baer wrote,

I consider the nucleus to be identical with that part which is usually called Wagner's spot . , . . Much later the part which is apparently considered an embryonic vesicle occupies a great part of the ovum. Because the small body shows, under pressure, a great resistance, the name "spot" is not so suitable. It seems to me very probable that the role which this nucleus (or embryonic spot) plays in the ovum of the sea urchin occurs in other animals in the embryonic vesicle. In addition to this, in the ovum of the sea urchin the part called embryonic vesicle disappears long before the end of maturation. (p. 238)

14. It must not be forgotten that even thirty years later O. Hertwig thought that during the maturation of the ovum the embryonic vesicle disappears, and the embryonic spot becomes the nucleus of the mature ovum (O. Hertwig, "Beitrage zur Kenntniss der Bildung, Befruchtung und Teilung des tierischen Eies," MORPH. JAHRB., I (1875) } III (1877) t IV, (1878) .

If the details of maturation remained unclear for Baer during the study of the processes of segmentation he could, despite his imperfect means of observation, see much and essentially move ahead of his contemporaries. According to Baer's description, after fertilization the ovum nucleus greatly submerges in the yolk and after some minutes it seems that it completely disappears. "However, under the microscope," Baer state, "the nucleus may be seen, although its boundaries are unclear due to uneven refraction of the surrounding granular yolk, Sometimes only a limited light radiance is seen. During the delivery of the ovum its boundaries, having the form of a circle, become more distinct" (p. 238).

Baer described the process of division itself in the following manner:

After the period of dormancy, the nucleus, having until then a spherical form, very quickly becomes elongated, and at the same time processes of protuberances appear from both of its sides. These ends of the nucleus swell, and its center becomes thin and is quickly torn off, so that two cometshaped nuclei with tails directed towards each other are formed. The tail-shaped appendage quickly extends inside its spherical mass, and then two nuclei are apparent .... Just before division the nucleus increases in size; at the time of division this increase progresses, so that each of the two new nuclei is approximately equal in size to the initial one .... Only after that, when both of the new nuclei are separated from each other, does the re twisting of the ovum begin, in consequence of which it is divided into two halves near to each other, each surrounded by its portion of yolk, (pp. 238-239)

Here Baer referred to Kolliker's paper. Since Kb'lliker did not doubt the complete disappearance of the embryonic vesicle, Baer, referring to his authority, left his own completely accurate observations in doubt and considered it necessary to check them again. Baer noted, however, that he could never ascertain the moment when the nucleus was completely absent. And what is more, he expressed confidence that in the ova of frogs the embryonic vesicle would be detectable in this period when, as it was believed, it completely disappears.

Further on, Baer passed to the description of the following stages of segmentation. Soon after the division of the ovum into two parts, "each nucleus begins by the way previously described to form processes, and changes by dividing in the middle into two new nuclei; the mass of yolk adjacent to it also is divided, so that all the ovum disintegrates into four masses. Each quarter becomes rounded, and in the center between them an empty space 16 is formed. The division of quadrants takes place completely similarly; moreover, the newly formed processes are situated at right angles to the previous ones. This continues also during the following divisions; moreover, for every new fragment of yolk a nucleus is formed by division of the earlier one,

Baer noted that the nucleus in the process of division is not always distinctly demarcated from the surrounding substance, "In the period of dormancy," Baer wrote, "a clear boundary line is seen under the microscope, but at the time of formation of the processes it cannot be observed with definition" (p. 239). Further, he drew from his observations another essential conclusion, concerning the method of formation of cells in the process of early embryonic development in the sea urchin. With great accuracy it can be established, and for subsequent divisions also, that when the nuclei are surrounded with a small layer of yolk the new cells are not formed "inside the maternal ones" ("yolk bodies," in Baer's terms) .

15. A. Kolliker, "Beitrage zur Entwickelungsgeschichte wirbelloser Thiere. 1: Uber die ersten Vorgange im befruchteten Ei," ARCH. ANAT . , PHYSIOL. (1843), pp. 68-141.

16. This rudiment of the division cavity (blastocoel) is called Baer's cavity by R. Remak.

Up to the stage of thirty-two blastomeres he could note directly the appearance of new blastomeres by division. Later on when they became numerous, it did not seem to be possible to trace the appearance of each, "However, here and there," Baer wrote, "in the yolk bodies, situated in the edge, the processes of division can be seen also as earlier. Even when the embryo leaves the ovum membrane and moves by the help of the cilia, every granule or each histogenic element (cell) possesses a very distinct nucleus" (p. 240), Baer could not trace the subsequent development, due to the movement of the embryo. Nevertheless, on the basis of the observations described above he reached the conclusion that later the histogenic elements (i.e. cells)result from earlier existing ones by means of the same kind of division. The general conclusion with which he ended the report stated: "The division of the yolk is considered only the beginning of the histogenetical separation, which continues uninterruptedly to the final formation of the animal. If this presentation is correct, then the question of the pre-existence of the new individual, before fertilization, is beyond any doubt. The unfertilized ovum is an embryo having latent life. The fertilization makes its life active" (p. 240),

This short paper of Baer's, as can be seen from its summary, contains an extremely rich content. There is no doubt that Baer saw with complete clarity all these processes of maturation and division of the ovum, which can be seen by intravital observations. He surpassed, by many decades, the views of his contemporaries, showing, first, that the nucleus of the fertilized ovum does not disappear, but becomes only less distinctly visible. He saw further the appearance of the radiant achromatic figures in the mitoses of division, the change at the time of their division, the disappearance of the nuclear membrane at the time of mitosis, and its appearance in interkinesis.

Drawings were not appended to the published report. If one looks at a picture of the division of the sea urchin ovum by intravital observation performed approximately a century later with an apochromatic objective and condenser, one will be surprised by the accuracy of Baer's observations and the insight of his discussion.

While his work on the history of development of invertebrates was not continued, Baer continued to the end of his life to be interested in the progress of the science of development and responded to every major event in this sphere.

The discovery, by N. P, Wagner of Kazan, of asexual reproduction in the larvae of diptera from the family Cecidomyidael7 evoked from Baer first a short report 18 and then a long paper. 19 Wagner found that from the ova laid by winged adults come large larvae, which, however, do not pupate. Inside each of these larvae a new generation of larvae develops, feeding on the fat body and other organs of the mother. Inside the larvae of the second generation the third generation originates and so on, resulting in an intermediate series of asexually formed generations. The larvae pupate and produce the dioecious winged cecidiums . The discovery of this unusual method of reproduction in dipters caused such great doubt that Siebold did not dare even to publish in the journal which he edited (ZEITSCHRIFT FUR WISSENSCHAFTLICHE ZOOLOGIE ) an article sent to him by Wagner .

17. N. P. Wagner, SPONTANEOUS REPRODUCTION OF CATERPILLARS AND INSECTS (Kazan, 1862) , 50 pp.

18. Baer, "Bericht (iber eine neue von Prof. Wagner in Kasan an Dipteren beobachtete abweichende Propagationsform," BULL. ACAD. SC. ST. PETERSB. (1863), 6, pp. 239-241.

19. Baer, "On the discovery by Professor Wagner of the asexual reproduction of larvae, on additional observations on this subject by G. Ganin, and on paedogenesis generally," Appendix to Vol. 10 of ZAPISOK IMP. AKAD NAUK (1866), No. 1, pp. 1-77.

Academicians Baer and Ovsyannikov personally were sure of the reliability of Wagner's observations, and he, after review by a committee that included Baer, Ovsyannikov, and Brandt, was awarded the Demidov prize. 20 i n the same year in Denmark Meinert21 confirmed Wagner's discovery, and proposed for cecidia, the larvae of which kill their mother during their development, the new generic name MIASTOR (Greek for killer, villain) . Meinert also agreed with Wagner that the larvae of the new generation arise from the fat body of the larva-mother. Pagenstecher22 also confirmed the fact of asexual reproduction among the larvae of cecidia, but he thought the larvae to be formed, not from the fat body, but from minute ova, but Pagenstecher could not establish the places of appearance of the ova.

The subsequent investigations of the reproduction of Miastors were performed in Leuckart's laboratory at Giessen; I. I. Mechnikov, who worked there, shared in them. In a preliminary report published in NATURALIST (No. 8, 1865), Mechnikov wrote that he, together with Leikart, found in the larvae of cecidia special organs — "small embryos, fissionable into separate compartments, swimming freely in the body cavity and producing new embryos. The development of the latter," Mechnikov continued, "I have also observed, and have found that the small embryos are formed from direct transformation of 'polar cells,' as in the genus Chironomus, as earlier blastomeres ." Baer especially underlined the importance of Mechnikov' s discovery, that "the small embryos or ovaries— call them what you will" are formed from special polar cells. "If the formation of the small embryos from these 'polar cells' is confirmed, then it will be an important increase of our expanded knowledge about the process of animal development" (p. 10). 23

20. Spontaneous reproduction of caterpillars and insects. Prof. Wagner. Kazan (Thirty- third Award of P. N. Demidov prize, June 26, 1864, pp. 238-242) (review by Baer together with Ovsyannikov and Brandt) .

21. F. Meinert, "Weitere Erlauterungen liber die von Prof, N. Wagner beschriebene Insektenlarve, welche sich durch Sprossenbildung vermehrt," ZEITSCHR. WISS. ZOOL. (1864) , 14, pp. 394-399.

22. A. Pagenstecher, "Die ungeschlechtliche Vermehrung der Fliegenlarven," ibid. , pp. 400-416.

Later Baer reported in detail the investigations of M. S. Ganin, ^4 prosector at Kharkov University. His observations are "extremely careful and circumspect, representing great interest." Describing in detail the structure of larvae, Ganin turned to their embryonic development; moreover, he reached the conclusion that the development of the young larvae inside the older ones did not arise from the fat body. He found an ovary, in which ova developed, giving the beginning to the young generation. Ganin thought that the ova of viviparous diptera that he investigated are differentiated from the ova of those insects which are characterized in the imaginal stage by the absence of the nucleus (Purkinje's vesicle) (117). Leuckart soon confirmed Ganin's observations concerning the development of Miastor ova within special organs, but he called these organs small embryos and not ovaries as Ganin called them. The developing group of cells in these small embryos are separated and fall in the body cavity. In each of these groups one cell increases in size and serves for the formation of the embryo, while the others, as in the embryonic chambers of other insects, play the role of feeding cells.

Baer considered it correct to distinguish the embryos identical with ova which are developed from ovaries producing true ova, and approved Leuckart 's suggestion of calling the early embryos of the Miastor false ova (PSEUDOVA) (118).

23. In the following year Mechnikov published detailed reports on the embryonic development of Miastor ("Uber die Entwickelung der viviparen Cecidomyidenlarve, nebst Bemerkungen iiber den Bau und die Fortpflanzung derselben," ibid . (1866) , 16, p. 407). In this paper the development of small embryos from polar cells was traced in detail .

24. M. Ganin, "Neue Beobachtungen liber die Fortpflanzung der viviparen Dipterenlarven," ibid . (1865), 15, p. 375; ZAP I SKI IMP. ACADEMII NAUK, 1865, 8, pp. 36-56.

Returning to Wagner's discovery, Baer mainly emphasized the distrust with which it was first viewed, "This circumstance," he stated, "shows to what extent the aforesaid discovery was unexpected and how little prepared we were for it. Subsequently, its importance lay in its proof, and credit was given to him" (pp. 22-23) . In connection with this he mentioned the words of Humboldt: "A book which, upon its appearance, immediately meets with general approval cannot be worth the publishing, because it can only conclude what already completely predominates in everyone's convictions." Illustrating this, Baer noted the discovery made by Peyssonel in 1723 that corals are animals, which "the great Reaumur rejected as an absurdity," so that Peyssonel could only publish it thirty years later. Further, Baer noted the fate of Harvey's discovery of blood circulation, which was subjected to doubt because "they did not know where air goes, it was assumed to exist in the arteries. The correctness of his discovery was recognized twenty years later, that is to say after Harvey's death. More time elapsed before the general recognition of Copernicus' discovery. The earth made its orbit around the sun many times before popes could speak of this publicly" (p. 24).

Baer remarked later that he did not mean to compare the discovery of asexual reproduction of larvae with the basis of the heliocentric theory; he wanted only to call attention to the frequently repeated historical relation of new ideas. He cited Agassi z, that each newly appearing study must pass through three phases: first they will say that it is incorrect, then that it is against religion, and finally that it had been known for a long time. "Wagner's discovery," Baer stated, "without doubt, does not need proof that it is not contrary to religion, or rather, dogma, for no dogma is concerned with fly larvae" (p. 25) . This discovery had already reached the stage of general recognition, the stage of coordinating it with previous opinions, for which it was necessary to change them somewhat. The idea must be rejected that the reproduction of posterity by means of fertilization, which is characteristic of man and other vertebrates, is a rule, and that all other forms of reproduction are exceptions. This idea is the source of the usual anthropomorphism, "man always standing at the center of his mental as well as his physical horizon" (p. 26).

Sexual reproduction, which is considered a necessity for the majority of animals, especially the higher ones, is intrinsic also to the plant kingdom, but in the latter it is not so necessary and frequently is changed into different forms of vegetative reproduction.

Referring to corresponding examples (potato, weeping willow, bulbous plants, and so on), Baer turned to the invertebrates, noting that in them also (for example, in Infusoria, Bryozoa, Ascidia, and polyps) reproduction by division and budding is very usual. Other forms of reproduction without fertilization, namely parthenogenesis, is characteristic among insects. The main form of parthenogenesis was considered Wagner's discovery of the Miastor. Contrary to the earlier known parthenogenesis, in which the source of ova developing without fertilization was thought to be the sexually mature females, in viviparous cecidia the embryos originate in the organism of the unformed larvae incapable of fertilization, Baer considered it advisable to give this form of reproduction a special name, and by analogy with parthenogenesis he termed it paedogenesis.25 i n both terms, Baer wrote, the first half of the word shows the producing subject. In a footnote he mentioned the correctness of Leuckart's note that the word parthenogenesis actually means the genesis o£ a virgin, and not genesis by a virgin; however, as this term became generally used, it was impossible to avoid analogy with it in the formation of a new record.

Comparing the phenomenon of parthenogenesis in Aphidae with paedogenesis in cecidia, Baer reached the conclusion that, as in Aphidae, the appearance of this or that form of reproduction (with fertilization or without it) is closely related to conditions of existence, in particular to intensity or nourishment; more abundant nutrition aids parthenogenetic and paedogenetic reproduction. The main conclusion to be drawn from the comparison of these forms of reproduction is that they both are an example of alternation of generations, or "alternating reproduction," during which sexual generation, i.e. by means of fertilization, alternates in one or more generations with reproduction without fertilization. To substantiate this conclusion Baer extracted material from Steenstrup's ftBER DEN GENERATIONSWECHSEL , 26 and other sources. He rated highly Steenstrup's work, in which the wide distribution of the phenomenon of alternation of generations is shown, which indicated its general biological significance. Baer turned his attention to the fact that Steenstrup had stated almost nothing about the alternation of generations in plants. Attempting to fill this gap, Baer cited many clear examples related to sporophytic and phanerogamous plants. These examples show that the alternation of two forms of reproduction — sexual and asexual (i.e. occurring without fertilization) — is inherent to the entire organic world. The alternation of generations, during which the ability to reproduce asexually appears (Baer related it not only to division, as in budding and other forms of vegetative reproduction, but also to development from unfertilized ova, i.e. parthenogenesis and paedogenesis) , he considered not an exception but a rule. The essential difference between sexual reproduction and all forms of asexual reproduction Baer concluded from the fact that sexual reproduction takes place only in the adult condition, while asexual reproduction occurs in different stages of ontogenesis. In particular, adult individuals are capable of parthenogenesis and reproduction by means of fertilization, while the paedogenesis of dipterous insects occurs only in larvae.

25. From the Greek P AIDES, meaning children,

The ability to reproduce in a sexually immature condition is characteristic also for other invertebrates — Coelenterata, parasitic Platyhelminthes, and Tunicata; therefore, all sexually immature forms of different animals — rediae, cercariae, brachiolariae, tornariae, strobiliae, scyphistomae, and so on—must also be called larvae.

In comparing the individual life of the organism — i.e. its development with reproduction — with the life of the species,

26. J. J. Steenstrup, (JBER DEN GENERATIONSWECHSEL, ODER DIE FORTPFLANZUNG DURCH ABWEICKENDE GENERATIONEN, EIN EIGENTHUMLICHE FORM DER BRUTSFLAGE IN DEN NIEDEREN THIERCLASSEN (Copenhagen, 1842), 140 pp. This edition represents the translation of Forentsen from a manuscript published at the same time in Danish.

Baer was concerned with the question of the relation of the instinct for self-preservation to the sexual instinct, and in connection with this he touched upon a question which worried him, on the possibility of including the understanding of purpose in a sphere of strict scientific investigation. His considerations are discussed below. 27

In the concluding chapter of his work Baer again noted the importance of the discovery of paedogenesis for understanding the idea of parthenogenesis and the alternation of generations. Understanding of these phenomena required systematic examination of different forms of reproduction. "I sought," Baer wrote, "to look through all that had been written on this subject, as in a consultation with myself— a consultation which may prompt more young investigators to attempt to make similar comparisons that would also be useful for them. During this, difficult tasks appear which we must trace more closely" (p. 70) . To these tasks Baer related the experimental investigations of the external conditions upon which the parthenogenesis of Aphidae and the paedogenesis of cecidia occurs. By means of these experiments, Baer supposed, it could be elucidated why, in apparently related species of medusa, one species immediately forms sexually mature medusa from the swimming larvae and the other goes through the sessile stage which is the budded strobila.

To these facts and considerations Baer gave the following resume:

Organic bodies possess the ability to self-develop by action intrinsic to them, as soon as they have the possibility of receiving the necessary material. In addition, they still have the ability to produce new individuals. (p, 72)

Self -development moves from absolutely simple forms and elementary parts by gradual transformations . „ . . The sequence of these changes is called in scientific terms development, and in ordinary term life, growth;

27. See Chapter 24

in addition, it means mainly the increase of body. But this increase in every separate vital process ceases early or late, although the tendency of self-preservation continues to exist, but the changes lead the organism to final dissociation. The capacity of reproduction, on the contrary, creates new individuals of this species, (p. 73)

The ability to reproduce is present in two forms. First, it may be considered a result of the necessary influence of one on the other of two materials .... This reproduction is called sexual , even in the case in which male and female sexual organs are present in the same individual. These individuals are called hermaphrodites. The second kind of reproduction is termed asexual reproduction. It is frequently seen in plants and the lower animals. Asexual reproduction in many organisms is found together with sexual reproduction .... This union of both kinds of reproduction can be called, according to Owen, metagenesis, or, according to Van Beneden, digenesis. The expression "alternation of generations". . . must be used only in those conditions when these forms of reproduction are alternated one with the other .... Sexual reproduction can never appear at the beginning of individual development, because the sexual organs must be formed early and secrete their products. The embryo produced by fertilization must always pass through all the stages of development intrinsic to this organism. When asexual reproduction takes place in the mature condition of the female individual, then it is called parthenogenesis. Similar reproduction in the immature condition we suggest calling paedogenesis. The latter may occur in all the different periods of development and may appear in very different forms, and also begins the course of development each time from the beginning, or may only continue it. (pp. 75-76)

From this it is clear that Baer established an orderly classification of the methods of reproduction, including all the organic world from the lower water plants to man, showing, in fact, the form of reproduction for evolution.

N, P, Wagner's discovery of the phenomenon of paedogenesis, which served as the starting point for Baer's discussions and also M, S. Ganin's detailed investigations in this topic, attracted Baer's intense attention. Because these works were considered evidence of the successes of Russian embryology, Baer always showed great care for its development. He energetically popularized works by Russian authors in his reports, published statements and letters. He was glad of the recognition of the importance of these works by influential investigators abroad and expressed the conviction that "there is yet no single route to us via the printing press and book trades" (p. 22).

It is interesting historically, however, that Baer's other great work, in which he posed the question, "Do the larvae of simple ascidiae develop initially like types of vertebrates?"^^ wa s very controversial.

The cause of his writing this paper was sensational . As Baer wrote, A. 0, Kovalevsky discovered that ascidians, which in their adult condition are so strongly differentiated from vertebrates, at the beginning develop similarly to vertebrates, "If this conclusion," Baer stated, "could have been substantiated, the sensation would have been completely valid, since Darwin's bold hypothesis that the higher organisms have evolved over the course of time from the lower, the lowest form differing absolutely from the highest, received great support" (p. 1) .

29 Outlining the content of Kovalevsky' s work, Baer again returned to the idea that "rigorous comparison of ascidian

28. Baer, "Entwickelt sich die Larve einfachen Ascidien in der ersten Zeit nach dem Typus der Wirbelthierefc" MEM. ACAD, IMP. SCIENCES ST. PETERSB, ,VII Ser (1873), 19, No. 8, pp. 1-35.

29. A Kovalevsky, "Entwicklungsgeschichte der einfachen Ascidien," ibid . (1866), 10, No. 15, 16 pp.

larvae with the early stages of vertebrates . . . apparently removes the difference between the main groups of the animal kingdom and makes obvious what has been accepted by many authors subsequent to Darwin, that the transition is made from lower forms into absolutely higher forms" (p. 3). How great the attention attracted by Kovalevsky's paper was, Baer judged by London's QUARTERLY JOURNAL OF MICROSCOPICAL SCIENCE, which as a rule printed only original papers, but made an exception for Kovalevsky's paper and published a translation of it practically in full.

30 Baer then referred to the investigation of I. I. Mechnikov,

"also an experienced embryologist," and in particular to the

data of K. Kupffer which he stated in a letter to M. Schultze

and which were confirmed by the latter, and attached to

Kupffer 's detailed article, "Already the name itself," Baer

wrote, "'the genetic relationship between Ascidiae and

vertebrates, '31 indicates the importance of the results received.

The factual data and Kovalevsky's interpretations concerning

the coincidence of the development of ascidiae and vertebrates,

were confirmed and partially made more accurate" (pp. 4-5).

Further on Baer noted this relation to Kovalevsky's discovery,

which Darwin had mentioned in THE DESCENT OF MAN, and cited

the following passage from this work:

Kovalevsky has lately observed that the larvae of Ascidians are related to the Vertebrata, in their manner of development, in the relative position of the nervous system, and in possessing a structure closely like the CHORDA DORSAL IS of vertebrate animals .... Thus, if we may rely on embryology, ever the safest guide classification, it seems that

30. I. Mechnikov, "Observations on the development of some animals (Bothryllus and solitary ascidiae)," IZV.

PETERSB. AKAD. NAUK (1869), 13, pp. 284-300.

31. K. v. Kupffer, "Die Stammverwandschaft zwischen Ascidien und wirbelthieren," ARCH. MIKR. ANAT . (1870), 6.

we have at last gained a clue to the source whence the Vertebrata were derived. We should then be justified in believing that at an extremely remote period a group of animals existed, resembling in many respects the larvae of our present Ascidians, which diverged into two great branches— the one retrograding in development and producing the present class of Ascidians, the other rising to the crown and summit of the animal kingdom by giving birth to the Vertebrata. 32

Baer cited after this only one negative treatment of Kovalevsky's discovery, 33 an d with characteristic honesty he drew attention to its groundlessness. Baer's objectivity stands out here more clearly, since he himself did not agree with the opinions of Kovalevsky, Kupffer, and Darwin. In the next twenty pages of his article, he brought all his learning and all his authority to bear on the idea of the relationship between tunicates and vertebrates and attempted to prove their systematic nearness to the bivalves, agreeing in this with Cuvier and basing his ideas upon the situation of siphons, nervous ganglia, and so on. Baer confirmed in particular that the side of the body where the nervous ganglion of ascidians is present is not the dorsal, but the ventral; therefore the nervous system of ascidians could not be homologous to the central nervous system of vertebrates. Later he discussed the cord in the caudal part in the larvae of ascidians and also refused to recognize its homology with the spinal cord of vertebrates. All polemics were sustained in very correct tones. Of his scientific opponents Baer everywhere spoke in a tone of complete respect to their scientific services and high competence.

Afterwards Baer explained why he went into anatomical details in this article, where it might better have been limited to brief reminiscence. "I meant," Baer wrote, "to show many dilettantes unconditionally believing in the possibility of transmutation and inclined to believe that the nonrecognition of ascidians as ancestors of man is attributable to sheer vanity" (p. 35) .

32. Charles Drawin, THE DESCENT OF MAN, AND SELECTION IN RELATION TO SEX. rev. ed. (New York, 1883),

pp. 159-160. Russian translation edited by I. M. Sechenov, S0CH.,Vol. 5 (Izd. AN SSSR, 1953), pp. 268-269.

33. ARCH. ANAT. PHYSIOL. (1870), p. 762.

The source of all his interpretations which were basically erroneous was Baer's view of the theory of evolution, in particular in relation to Darwinism. The discussion of Baer's views on evolution is beyond the scope of the present book. They did not appear in the literature; however, they have not been investigated sufficiently. But here it can be mentioned that Baer considered the evolutionary development of the organic world to be without doubt, but with known limits, having their sources in the theory of types established by him and Cuvier.

Stating the presence of transitional forms between the systematic groups within each of the four types, which testifies to the community of origin of all representatives of the type, Baer doubted that the signs of one type could be seen in the development of another type (119) .

Proceeding from this belief, Baer could not imagine that the tunicates, not having in the adult condition the general typical signs of the vertebrates, could show at any stage of development the characteristics of this type. From here there was a persistent striving from his side to give Kovalevsky's discovery this explanation, which did not stand in conflict with the theory of types.

Being considered the founder of embryological science, Baer did not leave behind him what could be called a school, In Konigsberg there were some young people who performed under his guidance dissertations on teratology, touching to some extent upon the history of development (120) . One Konigsberg student of Baer's, A. E. Grube (1812-1886), was later recommended by him to the Department of Zoology in Dorpat University. Grube published many works on zoology and comparative zoology; in addition he mainly studied annelids.

The influence of Baer's scientific interest is recognized first in the work Grube performed in Dorpat and published in 1844 (see Chapter 25), and also in the investigations of Majewski and Tschernow, whose dissertations were also defended at Dorpat University, in 1858. Both these dissertations illustrated the embryo-physiological problem of the chemical composition of the foetal fluids in mammals. Majewski34 (121) investigated the composition of the amniotic and allantoic fluids in twenty-eight embryos of sheep (four to thirteen weeks old) and in sixteen embryos of cattle (twelve to twenty-six weeks old), adding to this data concerning some embryos of swine and man. In this work he determined the weight, the length of the embryos studied, the quantity of amniotic and allantoic fluids, their specific gravity and reaction, and also the amount of solid constituents, either organic or inorganic, namely albumin, sugar, urea, phosphoric and sulphuric acids. In the tables of this dissertation, numbers are given for separate observations and average numbers for different periods of development. Majewski established that, according to the extent of formation of the embryo, the amount of the solid constituents in amniotic fluid increases. In particular, in all stages of intra-uterine life in all investigated animals and in man, the albumin and sugar are present in the amniotic fluid; the quantity of albumin shortly before birth somewhat decreases, and the quantity of sugar in the process of development of the embryo gradually increases, reaching the maximum before birth. The quantity of fluid in the allantois, and also the content of solid matter in it, increases with the development of the embryo. The allantoic fluid always remains transparent and similar to the saturated urine, while the quantity of urea in it gradually increases; in it there are also albumin and sugar. On the basis of his investigations, Majewski reached the conclusion that the amniotic fluid does not serve to feed the embryo, but protects it from external harmful influences and that the feeding of the foetus takes place only through the placenta.

34. Adolphus Majewski, polonus, DE SUBSTANTIARUM, QUAE LIQUORIBUS AMNII ET ALLANTOIDIS INSUNT, DIVERSIS VITAE EMBRYONALIS PERIODIS (Dorpat, 1858), 44 pp.

35 The thesis of Tschernow " (122) is a natural continuation

of the investigations of Majewski, which dealt with herbivorous animals, while Tschernow performed the study of the chemical composition of foetal fluids on carnivorous animals, mainly cats (he investigated forty-four foeti, weighing from 0,074 to 107,3 gm) . In addition, in his collection there were embryos of four dogs, nine swine, and one human, and also one horse embryo, which was used for comparison with carnivorous animals. Tschernow established that in the amniotic fluid the relation of the quantity of water to the solid constituents remains constant. In the allantois, the quantity of fluid in the process of foetal development gradually decreases, and simultaneously the relative quantity of water diminishes (from 989.5 to 949.8%), The amount of solid material in the fluid of the allantois increased at the expense of the organic matter (albumin— from 1.05 to 5.59%; sugar— from 0.95 to 2.02%; urea— from 1.48 to 12.10%). The albumin of allantoic fluid, according to Tschernow, is not necessarily secreted by the capillary renal vessels, although this possibility is not excluded, as the vessels of the foetus probably possess different permeability properties than the born animals, in whose urine there are no traces of albumin. Tschernow thought that albumin passes in the fluid of the allantois from the amniotic fluid, where it is always present. The sugar in the allantoic fluid of carnivores is significantly lower than in herbivores (in sheep, according to Majewski, it averages 7.57%, and in horses, according to Tschernow 's observations, it averages 11%), On the other hand, the urea in the allantoic fluid in carnivores is greater than in herbivorous animals.

The tradition of embryological investigations in Dorpat University, which is connected with the influence of Baer, remained. Thus, M. Braun, who was present from 1880 to 1886, in the beginning as a prosector of comparative anatomy and then as professor of zoology, worked on the embryology of bivalves, tapeworms, reptiles, birds, and mammals (among these works, investigations on the development of the wavy parrot

35. Nikolaus Tschernow (Estonus) , DE LTQUORUM EMBRYONALIUM IN ANIMALIBUS CARNIVORIS CONSTITUTION CHEMXCA (Dorpat, 1858) , 35 pp.

were distinguished) . Yu. Kennel replaced him in the department in 1887, He studied the embryology of Prototracheata and published three works on this topic.

The true successors of Baer as embryologists were, of course, A, 0. Kovalevsky and I. I. Mechnikov. Not formally students of Baer, they nonetheless paid high tribute to his classical investigations. To Kovalevsky and Mechnikov belong that unquestionable service of further development of Baer's studies and the creation of the theory of embryonic membranes, making the basis for comparative and evolutionary embryology.

Therefore, it was not by chance that in connection with Baer 1864 jubilee, the Academy of Science established a prize in his name for the best works on biological sciences. The first award of Baer's prize was received by Kovalevsky and Mechnikov. Baer himself participated in the discussion of candidates for the prize and expressed a patriotic pride on the occasion of its being awarded to Russian investigators.

In the conclusion of this chapter, some words must be stated about Baer as historian of embryology. Although he was not studying systematically the history of embryology, Baer stated many profound ideas about the development of this science. His discussions on this question are scattered through many works. Besides this, Baer subjected the literature of his prominent predecessor in the field of embryology, K. F. Wolff, to special study, and published a report on this work, 36 Baer's research concerning Tredern has been mentioned in Chapter 11.

References to the history of embryology in the works of Baer are always intimately connected with his own works; however, they frequently include an unusually large number of quotations from the works of his predecessors, and represent fragments of investigations in the field of history of science, showing a deep, thorough acquaintance with the literature (always from original sources) , and briefly describe the scientific epoch or direction of scientific thought ,

36. Baer, "Uber den litterarischen Nachlass von C. F. Wolff, ehemaligem Mitglied der Akademie der Wissenschaften zu St. Petersburg," BULL. CL . PHYS.-MATH. AC. ST. PETERSB. (1846), 5, No. 9, 10, pp. 129-160.

Chapter 24. On the Question of Baer's Theoretical Views

For the exhaustive characteristics of Baer's views, it is necessary to consider all his papers and correspondence with regard to published and archival materials. This task is a matter for the future. Until now, discussions of Baer's theoretical views as a rule have been limited to evaluation of his scientific work. Therefore, all opinions up to the present about Baer's philosophical views have made a common mistake, for which the authors cannot always be blamed. Their errors could result in part from the fact that Baer was sometimes undoubtedly forced to present his thoughts in a form adapted to the censors' requirements of his time. As for articles published in the Russian language, the possibility must also be considered that the translation from the German original, as it was written by Baer, was misrepresented.

But regardless of these circumstances, the well-founded discussion about Baer's methodical views is difficult to dispute. The spiritual personality of the great naturalist was too complicated and multifaceted to determine the essence of his views easily and at the same time to state the changes which were made during his long years of scientific activity.

Baer did not avoid stating his opinions concerning general questions, beginning with the earliest work, such as the article "Two Words on the Recent Condition of Natural History,"! and ending with the general philosophical conclusions of SPEECHES AND ARTICLES (1864-1876). In striving for a description of Baer's theoretical views, one must turn to his own discussions on the general questions of philosophy

1. K, E. v. Baer, "Zwei Worte uber den jetzigen Zustand der Naturgeschichte," Vortage bei Gelegenheit der Errichtung eines zoologischen Museums in Konigsberg (1821) , 48 pp.

489

and natural sciences. But they should not be considered satisfactory, and hence they may represent falsification (123), The latter is correct, in particular, in relation to R. Stolzle, professor of philosophy at Wurzburg, who wrote a vast work in 1897 under the title KARL -ERNST VON BAER AND HIS WORLD-VIEW. 2 From the beginning Stolzle stated that in his book he would judge Baer from a theistic-Christian standpoint; he lamented that this point of view, especially in the natural-scientific and philosophical circles of his day, was generally ridiculed as being absolutely unscientific, and either regarded as an anachronism or simply disregarded. 3 Stolzle praised Baer for his world-view and unconditionally set him up against evolution, teleology and idealism. However, at the same time he remarks, apparently indignantly, upon the "errors" of the great scientist concerning Baer's sharp opinions against creationism. Stolzle wrote, for example, of the "barely respectable polemics of Baer against the idea of a creator" and cited his ironical discussion of the origin of new classes of animals on the earth: "I do not want to trouble Our Lord with this 'creation of new classes,' for if he wishes to throw down from the sky a new class of animals on earth, then they must, due to the quick motion of the earth— four miles per second! and this is not a joke — shatter into dust. Our Lord, therefore, must come down to the earth and arrest its velocity; only then can he create new living creatures. "4

Actually, in the concluding chapter of his book, Stolzle "absolved" Baer for all his "inconsistencies" and for all his "errors," assuming that Baer "at the end turned to faith in the ever-living God; probably this may confirm

2. R. Stolzle, KARL ERNST VON BAER UND SEINE WELTANSCHAUUNG (Regensburg, 1897), xi + 687 pp.

3. Ibid. , p. 5. Haake, in his work on Baer (W. Haake, KARL ERNST VON BAER (Klassiker der Naturwissenschaften) (Leipzig, 1905), 175 pp.), also extolled Baer for his supposedly high evaluation of the religious need of man.

4. stolzle, KARL ERNST VON BAER, p. 167.

490

also (his) faith in Christ. "^ Stolzle took this confidence from journal articles, based on information from a Pastor Engelhardt. The later asserted that on his deathbed Baer regretted his unbelief. The foolishness of this idea was documented not long ago by B. E. Raikov. 6

Also, contentious and groundless discussions of Baer's philosophical ideas were given by Stolzle. Their source was explained by him as Schelling's natural philosophy, which at the beginning of the nineteenth century had received very wide distribution among naturalists. About the wreck of natural philosophy, Stolzle correctly wrote. Instead of the fantastic opinions which fear experiments, come sober ideas which are based on experiments instead of intuition, on the firm and slow work of induction in place of metaphysics — either the rejection of all that is transcendent, as in the ideas of Francis Bacon, as also in the ideas of Kant and Comte, or materialism. 7 Talking of Baer's earlier interest in Naturphilosophie and even mentioning his ironic references to the lecture of Wagner, Stolzle nevertheless remarked that

5. Ibid . , p. 644.

6. B. E. Raikov, "Poslednie dni Baera" (Baer's last days) , TRUDY INSTITUTA ISTORII ESTESTVOZNANIYA AN SSSR,

2 (1948) , pp. 575-583.

If it could not be doubted that church orthodoxy was alien to Baer throughout his life, then it would be difficult to state with confidence his relation to deistic thought. In his writings, especially in his popular scientific discussions, one finds theories of creation as first origin of all beings. See, for example, the series of articles under the common title "Man's Place in Nature," published in NATURALIST, Vol. II (1865), Nos. 2, 3, 4, 19, 20, 21, 22, 23, and 24; Vol. Ill (1866), Nos. 9, 18, 22, 23, and 24; Vol. IV (1867), Nos. 1, 2, and 3. These articles, according to B. E. Raikov, were strongly misrepresented by the censor.

In these articles, and also in his German- language article "On the Doctrine of Darwin" ("Uber Darwin's Lehre," REDEN . . . UND KLEINERE AUFSATZE, II, pp. 235-480). Baer argued against Darwin and his followers (mainly against T. Huxley) on the question of the origin of man, decisively

(Footnotes continued on next page)

491

Baer "did not throw out the baby with the bathwater, and while discussing the false path into which Naturphilosophie had been enticed, he recognized it as a source for a deeper understanding of nature. "8

For the proof of this statement, Stolzle referred to the following view by Baer which he stated in his earliest theoretical writing, "Zwei Worte uber den jetzigen Zustand der Naturgeschichte": "In spite of the giddiness experienced by the nature-philosophers, the world nevertheless must move with inevitability in itself, because this takes place in reality. With this, frequently and not very seriously, they made merry, exclaiming: 'We shall only hold on to the earth more strongly, then our heads will not whirl.* It seems to us, on the contrary, that all the significant progress in science is inevitably accompanied by fever, and during fever there are frequently dreams and apparitions. The experienced doctor is sometimes satisfied with the course of fever in his patient if he notices in it the preparation for a crisis, "9

6... rejecting the possibility of his development from any of the other living species of monkeys. In addition to strictly scientific reasons from the field of comparative anatomy and comparative psychology, there are also appeals to common sense, hindering, in Baer's opinion, recognition of an animal origin for man. In discussions concerning the evolution of the organic world and especially the origin of man, Baer undoubtedly did not overcome the religious faction, and was even inclined to renounce his partial recognition of the idea of evolution, which he had stated many years before this.

7. Stolzle, KARL ERNST VON BAER, p. 36.

8. Ibid ., p. 39.

9. Baer, "Zwei Worte," p. 4G.

492

^4U

V ^£

•'^^fiQf&g)---*©---* — ° — •

ficbcn

gtt>altcn

in ttJi(fcnfd)fif{iid|cn Strfammlnngtu

unb

kUiure ^nffa%r oermifdyten 3uljolt6

Dr. iUrf ^mll i>. ^Sak,

Jtmi«ii|lit» rn »«Oni.»<. tfitcnx fn S>iA«il*«'tni 10 € i *«frl»«t« 

€ r ft r r 8 h r i I ifcbtn.

dill Hm MMlJ Sf» r«l|alf»r» IH '.HUD,*

.9**

6t. frtnfbBrg. 1864.

rlilbtn ^pfbu*ba»Miinci V 1 ift.n BIiiimi

fl Stilaq txi ffaifrrliifcrn ^efhuAbanftlmiq V ^*miptonl

i*«ii BIiiimi

-^„t

Figure 35. The title page of the collection REDEN...UND KLEINERE AUFSATZE by K. M. Baer f with his autograph; presented by Baer to the Moscow Society of Nature Investigators.

493

From these examples of speeches it is possible to conclude that in his early years Baer was already an opponent of the collection of facts not illustrated by theoretical generalization. Of the importance for science of both empirical and theoretical investigation and of their relation, Baer wrote in the same article: "There are two ways in which natural science can succeed: observation and meditation. The investigator goes into the majority of cases in one of these ways. Some of them are thirsty for facts, others for results and general laws; some of them for information, others for knowledge; the first can be called the careful investigators and the latter the serious ones. Fortunately, the human mind is rarely developed so one-sidedly that he uses only one way of investigation, disregarding the other. Despised abstraction at the time of his observations involuntarily leads to meditation, and his opponent only in the short period of fever can be engaged in speculations in the sphere of natural science, absolutely disregarding the data of the experiment. For the individual personality, as well as for an entire age of science, one tendency may be predominant and the objectives follow it consciously, but the other is not excluded completely. ,?1

These two sides of scientific investigation — experiment and theoretical discussion, observation and meditation — were always taken into consideration by Baer, and he put them in the form of a subtitle sounding like an epigraph to his great work: (JBER ENTWICKLUNGSGESCHICHTE DER THIERE: BEOBACHTUNG UND REFLEXTION. It is not by chance, however, that here, as in other cases, observation is put before meditation. One can reflect only upon what has already been observed; Baer did not recognize any a priori truths. 11

"Investigation of nature," Baer wrote, "in general must start from the observation of individual phenomena, and the latter only in that extent are combined into a universal authenticity, as far as this allows. There also, where it

10. Ibid. , p. 31.

11. In this idea he made an exception only for mathematics

494

1 2 ends, ignorance begins. " x Elsewhere he stated that the

history of science is a long commentary on the situation that the material for one's knowledge of the outer world is collected by detailed observation, and that these are processed by the natural ability of meditation. No discovery is done a priori. "I doubt that man would have, in general, any information about the existence of the world, if he did not make certain of it by his senses. "H

The statement that the endlessly variable world exists independently of our consciousness, and is perceived by means of the organs of sense, was connected in Baer with confidence in the unlimited cognitive power of human intelligence and his creation, the sciences. As to the question of the importance of science, Baer repeatedly clothed his discussion either in a pathetic or a sarcastic form.

"Science," Baer stated, "is eternal in its source, not limited in its activity either by time, or by distance, immeasurable in its size, endless in its tasks, unachievable in its aims. "14 This aphorism, especially its Russian translation published in the journal of the Ministry of Public Education and not re-edited by Baer, needs some explanation. Baer spoke of science "eternal in its source" (EWIG IN IHREM QUELLE) ,15 i. e . having its source in eternal nature, but the translator turned it into science "resulting from eternal beginnings," i.e. as if having its source in relevation. Speaking of the unachievability of aims in science, Baer undoubtedly meant the impossibility of exhausting by scientific knowledge the endless variable phenomena of the world, and not the presence in it of anything beyond the grasp of the mind. That this interpretation of Baer's ideas is correct is confirmed to other places. For example, in the speech, "View on the Development of Science,"

12. Baer, "Uber Zielstrebigkeit in den organischen Korpern

insbesondere," REDEN, II, 2te Aufl. (1886), pp. 170-234.

13 • Akad. ber Vzglyed na razvitie nauk. Zhurn. Min. NarProsv., May 1836, p. 207.

14. Ibid ., p. 245.

15. Baer, "Blicke auf die Entwickelung der Wissenschaft," REDEN, I, 2nd ed., p. 121.

495

Baer wrote: "... The limited minds cherished the hope, or rather expressed the apprehension, that the limits of human knowledge will soon be achieved. The idea is cowardly, unworthy of the endless productivity of the human intelligence."^

The attention of many authors, attempting to interpret Baer's viewpoints either from orthodox theological and idealistic positions, or from materialistic positions, was mainly attracted by by his discussion concerning purpose in nature in general and in particular in the organic world. Baer illustrated these questions in two vast articles published in the second volumes of his REDEN UND KLEINERE AUFSATZE. In order to form a presentation of Baer's real views on the problem of purpose, especially in individual development, it is necessary to turn to the articles mentioned and look at the details of their terminology. Only then will it be possible to attempt to determine what arises from Baer's spontaneous materialism and what amid the health of his ideas must be considered idealistic slag.

The first of these articles is called "On Purpose in the Phenomena of Nature. "1? It begins with the assertion that naturalists are extremely worried about the recognition of purpose in the processes and products of nature. In order to make this account completely clear, Baer considered it necessary to come first to an understanding about the application of the concept. He began with the word "nature," which means all that really exists and arises without the participation of human skill. The last is especially important to bear in mind, because all that exists was placed, was made through formation as it is presently. The solid rock as well as the changing cloud are both the results of a development process. But the correctness of this idea is especially confirmed by organic bodies, which are present in a condition change. The present condition of an organism became possible

16. Baer, "View of the Development of Science," p. 194.

17. Baer, "Uber den Zweck in den Vorgangen der Natur. Erste Abtheilung: Uber Zweckmassigkeit Oder Zielstrebigkeit uberhaupt," REDEN, II, p. 49-105.

496

only in connection with the previous and the future conditions, in connection with the present. The essence of life itself is considered the course of the vital process, i.e. a series of conditions following one after the other. Of the source of this change, Baer spoke with a certainty excluding all doubt.

We cannot leave without discussing the idle argument about the vital power, that matter goes only by necessity, causing all the momentary conditions of organization that follow one after the other .... In order to make this more obvious , we say that in organic life, each separate condition is only a momentary expression of formation, or that the settled condition is only a making visible, and that formation is essence and permanence . 18

The latter condition is the consequence of the previous, not only by time, but also in relation to their internal conditions. To illustrate, Baer mentioned the example of the butterfly, whose imaginal condition is anticipated and conditioned by the pupa stage, the condition of the pupa by the caterpillar stage, the condition of the caterpillar by the stage of the ovum appearing in the mother. The source of material for all these transformations is, according to Baer, the plant food used by the caterpillar. The materials taken up as food are processed in the caterpillar into reserve products which are used in the following conditions. The vital process of the developed insect "needs food — we call this demand hunger — thus, it demands enough food to suffice it not only for the intensive growth of the caterpillar, but also for the creation of reserves for future stages. "19

Baer especially underlined the connection of these conditions, processes and preparatory changes with the final condition; in their resulting "from a spherical or ellipsoidal

18. Ibid . , pp. 52-53. The same idea was stated by Baer in the speech "Welche Auf f assung der lebenden Natur ist richtige ' delivered at the opening of the Russian Entomological Society in 1860 (REDEN, I, 1864, p. 268).

19. Ibid ., pp. 53-54.

497

ovum through many intermediate stages the final goal (ZEIL) is reached— the fluttering butterfly. "20 "The more we enter into details, the more completely this special relation (ZWECKBEZIEHUNG) appears. It must be noted that for the work which must be performed in each separate condition, all necessary instruments are not only present at the necessary time, but are formed in the previous condition. "21

"Themaxillae and extremities of the caterpillar, which are adapted to its form of life, are developed in the ovum, so that from the moment of hatching everything necessary for the function of intensive feeding is already prepared. The organs of the butterfly— wings, long legs and spiral proboscis — are developed in the pupa stage, i.e. long before these organs will be used. Within the hard shell of the pupa, internal transformations take place which are completely connected with the future and not with the present. "22

Baer also discussed this question in detail in the second article, considering the continuation of the work "On Purpose in the Phenomena of Nature" and entitled "On the Trend of Processes, Especially in Organic Bodies. "23

Speaking of embryonic development, he noted that already in the earliest stages the material of the ovum is processed for the formation of organs, so that development proceeds "as if there sits in the ovum a judicious and understanding builder. "24 This metaphor was necessary to underline that from his point of view the vital process in particular' and the development of the individual is characterized by a trend towards a definite end, although the ovum and the developed embryos, of course, do not recognize this end. Here Baer also had mentioned that the trend of development is not absolute, but adapted to surrounding conditions; thus, the eggs of birds require the effect of heat and the free flow of air. The necessity for determined conditions for development is shown also by other animals; their life, i.e.

20. Ibid ., p. 54.

21. Ibid ., p. 55.

22. Ibid., g. 53.

23. Baer, "Uber Zielstrebigkeit. "

24. Ibid ., p. 228.

498

continuous internal preformation, can take place only during suitable external conditions. "Life," Baer wrote, "is nothing other than a movement towards a definite final selftransformation, adapted to external conditions." To illustrate, Baer described the early stages of development of the eggs of the hen, of the frog, and of the sea urchin, and also described the behavior connected with reproduction.

From the actual data cited, he concluded the following. The physico-chemical processes in the early stages of development, when their direction appears, have been studied very insufficiently. In the vertebrate embryo, two shafts ascend on the dorsal side which are then united in a tube; the results and the significance of this process is clear: the central nervous system is formed from the internal layer of the tube, and from the external layer the bones, muscles, and skin are formed. "Thus, in relation to this process, the question why is very easy to answer, and the question, by what means does it happen, remains completely open for the naturalist. Naturally, one doubts that this process is conditioned by physical necessity, since the end of any process is reached only on the basis of the laws of nature; without reference to the latter, any phenomenon must be considered magic. "25

"I can then repeat the question," Baer continued, "how is it possible to overemphasize that all these processes are related to future requirements? They are directed to what must originate. Philosophers who wrote in Latin called this relation causa finalis , or final cause (ZIEL) .... And in all other animals the changes following one after another must serve a purpose (ZWECKSINNLICH SEIN)." 26 For the exact understanding of Baer's idea it is necessary to review his terminology. In the German language there are two words — ZWECK and ZIEL — which are both translated into the Russian language as "purpose"; as a matter of fact, in the normal German usage as well, these words can replace each other. However, Baer found in them this shade of meaning; he considered it possible to use them for the designation of different concepts, proceeding from the following considerations

25. Ibid ., £. 192.

26. Baer, "Uber den Zweck," p. 51

499

A large part of psychological terminology is based on the use of spatial, generally sensory perceptions. "We speak about deep or superficial ideas, about difficult and easy problems, about obscure and clear ideas, about strong, weak, hard-hearted and gentle characters, and so on. 2 ^ If in the language a word appears to designate a psychological condition, then, of course, it concerns man. This, in particular, relates to the word ZWECK. 2 ^ For the achievement of purpose by man it is necessary and advisable for him to select his means. There are people who devise excellent aims for themselves, but do not achieve them, because they use inadvisable means. On the contrary, in relation to many phenomena of nature, even if they end with a definite result, it is impossible to claim that they result from an aim determined by an intelligent being. According to Baer, the result of separate processes can be designated by the word ZIEL, which does not assume the involvement of judicious consciousness. ZIEL is the end of motion; its achievement is completely based upon necessity. "Sending the arrow or bullet into the target (ZIEL) I use mechanical powers in the necessary proportions and I orient them in a definite direction. The purpose which I am pursuing in this case I can hold in front of me and, if all is correctly calculated, an arrow must of necessity fly

27. Ibid . , p. 74.

28. The Russian translation of the words ZWECK, ZIEL, and their derivatives are connected by known convention. Hereafter, ZWECK, ZWECKMASSIC, and ZWECMASSIGKEITwi.il be designated by the words "purpose," "expedient," and "expediency." For the designation of the concept ZIEL, after many attempts to select a more successful word, we settled on "final end," using in many cases the words "trend," "end," "target" (followed throughout by ZIEL in brackets) ; ZIELSTREBIG is translated as "definitely directed," "going or acting in a definite direction"; ZIELSTREBIGKEIT is translated as "direction," "definite direction."

500

29 into the target (ZIEL), regardless of the purpose (ZWECK)."

Therefore, for natural phenomena, Baer proposed to use the

expressions ZIEL, ZIELSTREBIG, ZIELSTREBIGKEIT instead of

ZWECK, ZWECKMASSIG, ZWECKMASSIGKEIT, as the first

expressions are free of that shade of meaning which expresses

the adoption of a conscious decision.

These considerations Baer illustrated by the following example: "In saying that the new-laid egg has the purpose to be a hen, I can be asked how. Is there in it a creature possessing creative powers and will? If it is also stated that this egg is predetermined to form a chicken, then with this all will agree, because it is known that the egg is formed in a natural way and possesses an ability of necessity to form a chicken, of course given the suitable temperature."-^ The presence of a definite direction of development, predetermined by the structure of the egg, Baer called the final end (ZIEL), and did not mean here conscious purpose, when actually there is no sense in searching for it, neither in the yolk nor in the albumin. The purpose (ZWECK) , in his opinion, must be sought in much earlier stages, in the ability of organic bodies to give rise to new individuals of the same species. Baer designated final goal (ZIEL) not only as the result of activity, the end towards which something moves (in the present case, transformation at the time of development) , but he meant the forced necessity which acts in a definite direction.

In the article "Uber Zieletrebigkeit in den organischen Kdrpern," Baer returned to definite concepts. He wrote: "ZWECK is a consciously determined task, ZIEL is the given direction of the action; ZWECK is the source of freedom, ZIEL is an outlined success which may be achieved by means of necessity. If we apply this understanding to nature, then naturally we cannot attribute to it any purpose (ZWECK) ; however, it is unconditionally impossible to disclaim trend or direction. Each organism in the process of formation is characterized by a direction and a final goal (ZIEL) of this process. "31

29. Baer, "Uber den Zweck," p. 186.

30. Ibid ., £. 83.

31. Baer, "Uber Zielstrebigkeit, " p. 180.

501

Later, Baer asked why the mention of processes which serve purposes is met by naturalists with such distrust, and whether there is any real basis for this distrust. In order to answer this question, Baer turned to the history of natural science. Man first sought to solve the most common problems, and only later did he learn to open up questions and pose them so that he could give concrete answers. Thus, at the beginning, the ancient Greeks proposed many hypotheses about the origin and existence of the world. Only gradually did they begin to observe reality and to meditate upon the processes of nature. They established that in nature there are known powers or regularities acting. The Romans added very little to that which had been known by the Greeks, and gradually showed little inclination to present new methods in the field of science. Meanwhile, as other peoples of Europe emerged from the state of barbarism, a characteristic religion spread which for a long time devoured all spiritual inquiries. When this religion became dominant in Byzantium and Rome, a powerful priesthood worried about whether men in their scientific aspirations followed the course outlined for them by the church. As a result of this, for a long time in the natural sciences there was no noticeable progress. The discovery of America and of previously unknown living beings, the discovery of a sea route to India, the ideological interpretations of the epoch of the Reformation, and, mainly, Copernicus' proof of the earth's rotation around its axis and around the sun, regardless of the evidence of vision — all this aided the powerful increase of scientific interest and provoked the independence of ideas and their critical relation to authority.

However, the scientific struggle kept its medieval character for a long time. Many absolutely groundless statements were put forward; thus, in the structure of the organism it was desirable first of all to see the intention of the Creator. In accordance with the studies of the Christian religion, seeing a spiritual beginning in all activities, they searched for the acting power everywhere. Even in the middle of the seventeenth century, Fabricius ab Aquapendente, in a work illustrating the development of the hen's egg, declared the existence of six forces upon which the formation of the chick depends. However, in his actual observation he committed very flagrant errors . From the beginning of the sixteenth century, the study of anatomy

502

became animated. For a very long time students had only repeated what was known to the ancient Greeks. In the study of the structure of organisms, they everywhere collided with the manifestation of purpose, whose existence, as all else, was attributed to the omnipotent Creator. Thus, one teacher stated that he illustrated the effect of the wisdom of God, in that God, in his opinion, directed the flow of the rivers to where the big cities are. In other cases a purely mechanical necessity was attached to this idea. Spiegel, 32 a seventeenth- century anatomist, speaking of the sciatic muscles in man, which develop more in connection with the direct process of walking than in other animals, stated his belief that man possesses such powerful sciatic muscles so that he may sit on soft bedding when he meditates on the greatness of God. "Another anatomist," according to Baer, "posed the question, why does man not have two backs, and answered, because that would be ridiculous. "33 The new method was established by Newton and his contemporaries, showing the application of the fall of bodies and the movement of the planets to simple laws of nature and their effect. Only then did "the powers contrived from a scarcity of knowledge, about which it was impossible to state anydefinite thing . . . disappear as ghosts in the light. "34

"At the end of the eighteenth century," Baer wrote in his article "Uber Zielstrebigkeit," "man did not doubt that all physico-chemical processes are under obligation to natural necessity. "35

Otherwise at that time they were related to vital manifestations, the supposition being that they obeyed special regularities absolutely. In relation to living beings it was considered necessary to take into consideration "a special power which shows its activity on these bodies and all conditions which could not be explained with the help of the already known physical and chemical powers; this power

32. Adriaan van den Spiegel, Dutch anatomist and embryologist

(1578-1625). He wrote DE FORMATU FOETU (Amsterdam, 1645) .

33. Baer, "Uber den Zweck," p. 62.

34. Ibid ., £.64.

35. Baer, "Uber Zielstrebigkeit," p. 186.

503

was called the vital power. All different activities must be attributed to it; it must not only expediently build the body, but also must prevent the disturbance of its building by disease or injury; it must select from the substances of the surrounding world those which are necessary for building up the body and supporting life. Thus, nothing such as the activity of the mind was attributed to it, because it must act in accordance with purpose. Later this idea contrasted with another idea widely distributed in the nineteenth century. This latter stated that the vital power is only a result of fantasy, invented to cover ignorance. The vital process is a physicochemical process so complicated that, after a long time, we still cannot break it down into its separate components; as a whole it exists by physico-chemical laws, i.e. it arises by strict necessity. The most diligent supporters of this idea added that about the purpose and trend of vital phenomena there must not be any speech. "36 Concerning the idea of the vital power, Baer absolutely agreed with the assertion that it must be regarded as an attempt to obscure an inability to solve a problem.

A power to which it is impossible to add measures, a power which strives for the final end which is a result of fantasy of a production of ideas .... The organism, undoubtedly, is considered a mechanical apparatus , a machine that builds itself. The vital process takes place by means of continuous physico-chemical processes; as a result of this the organism can be called a chemical laboratory, although at the same time it can also be considered a laboratory technician .... Regardless of the achievements in knowledge of individual processes in the organism, nothing remains directed and predominated on physico-chemical processes in them, namely life itself.

It is absolutely natural that now everything is investigated from the point of view of

36. Ibid., p. 187

504

unconditional necessity, and I consider this direction absolutely correct .... The physics and chemistry of our time reap their fruits. With the help of these sciences they sought to interpret the vital phenomena of plants and animals also as a physico-chemical process which arises for each organic form by special means? by these ways many things already can be explained, and it can be hoped ,_ that present problems with time will be solved.

However, Baer considered that success in the knowledge of nature's processes, appearing as a necessary activity, must not lead to denying direction and purpose (ZIELE UND ZWECKE) in nature. Baer did not agree with the opinion of those who considered that teleological opinion in the study of nature is absolutely unsuitable and that in nature there is neither direction nor purpose (WEDER ZIELE NOCH ZWECKE). "Teleology," Baer stated, "is the study of direction (ZIEL), 58 and thus purpose (ZWECK) and the final end (ZIEL) are also present; then teleology is a study of the objective relations in natural phenomena. I can never be sure of the absence of all direction, or consider the question as ridiculous or shameful. "39

Baer discussed Haeckel's opinion from his GENERAL MORPHOLOGY that chance and purpose are absent in nature and only absolute necessity predominates (compulsion). Baer considered it erroneous to contrast necessity and purpose, because in his opinion purpose is reached by means of necessity.

The marble statue, it is known, is built by mechanical means. Absolute necessity consists in that the marble block is beaten by hammer and

37. Baer, "Uber den Zweck," pp. 64-65.

38. In a footnote Baer explained that "the Greek word TeAos (end, outcome, result — L.B.) is in German designated ZIEL

39. Baer, "Uber den Zweck," p. 65. From this extract it will be seen that Baer has confused his differentiations between ZIEL and ZWECK.

505

chisel as much as by necessity for it's transformation into a human figure. However, when the production of art is present before us, we must recognize that all the necessities used served only for realizing the idea of the artist, and his purpose (ZWECK) .40

Baer thought that the process of formation must not be credited to the effect of powers, but that the powers must be measured in accordance with the final end (ZIEL) , or they will not build anything and can only destroy.

In another instance, Baer noted that naturalists who dread purpose or direction have a confusion of ideas. The naturalist must put the question to nature: "how?" or "what?" Then, "due to what?" And finally "why, or what for?" For the answer to the questions how and what, he investigates the acting conditions and finds the necessities which he calls laws of nature. If the effect of necessity is not definitely directed (ZIELSTREBEND) , then the vital process cannot be realized. The question why or for what is related to the study of this trend (ZIELSTREBIGKEIT) . This question, in Baer's opinion, is absolutely lawful for the complete understanding of the phenomenon. It produces misgivings because in past centuries, when men believed in the omnipotent nature of God, above natural law, they answered the question why with reference to the direction of the process, and imagined it not as being realized by means of necessity, but as a human purpose, reached by conscious will. The investigation of animal embryology is considered that branch of nature study where the direction of processes stands out especially clearly, because the organic, body is regarded in its formation. The processes of formation are definitely directed (Z IELSTREBIG) , they arise from their result; they, of course, are conditioned by necessity. In Baer's opinion, however, it would have been scientific superstition to consider that one could speak about the necessity of the progressing phenomena without turning attention to their direction

40. Ibid., p. 69.

506

(ZIEL). It must only be remembered, Raer stated, that the final end (ZIEL) is achieved not by intelligent will, but by means of necessity.

"In the elucidation of how life in nature is formed from necessities, leading to a definite final end (ZIELSTREBICE NOTWENDIGKEITEN), and from the directed processes conditioned by necessity (NOTWENDIG VERFOLGTEN ZIELEN), it seems to me the true task of the study of nature is concluded. "41

"If the old wisdom," Baer states, "which recognizes expediency and greatness in the activities of nature, must be rejected, after it has been explained that the opinions on which it is based are too intimately connected with human behavior, this does not give one the right to assert that in nature the necessities act alone, devoid of direction (ZIEL). It is absolutely clear that nothing takes place without basis; however, indirected forces of nature cannot build any regulated thing, not even a mathematically defined form and even less a complicated organism; they can only destroy. "42

Mentioning many examples of expediency (corresponding to necessity) of organization of living creatures and indistinctly forming the idea of progressive evolution, whose crown is considered the wise man, Baer cited his statement of thirty-three years earlier, invested in idealistic form: "The earthly body is only a bed, on which the hereditary spiritual resplendence of man develops. The history of nature is only a history of the progressive victory of the spirit over matter. "43 After Baer's statement of theoretical opinions about the phenomenon of individual development, it is permissible to posit a question about the essence of his outlook.

It is decidedly necessary to mark off Baer's opinions from the reactionary idealism of Stolzle, Kelmersen, and others who insisted on the identity of Baer's ideas with

41. Ibid ., p. 73.

42. Ibid ., p. 88.

43. Baer, "Das allgemeinste Gesetz der Natur in aller Entwickelung," REDEN, I, 2nd ed. (1886), pp. 71-72.

507

their own opinions. Similar evaluation of Baer's views in many cases depends upon an arbitrary interpretation of his separate discussions, sometimes pulled out of context: in addition to this, this evaluation does not reflect the contradictions within Baer's views, so natural in his era, when religious dogma and philosophical idealism resisted the tendency to interpret natural phenomena by a simplified materialism.

In the remarks on his list of works published in his autobiography, in particular in the remarks to UBER ENTWICKLUNGSGESCHICHTE, Baer wrote:

On the subject of my general opinions situated in both parts of this work, the reproach was made that they were too mechanical . I confess that I take this reproach for praise , because it is better to stand on solid ground than to be up in the clouds . For the naturalistic point of view the rule generally answers of talking only about what I have really seen, and concluding ideas from observations, and not basing observations on preconceived ideas. That is what I took for myself from the rule. ^

Baer's philosophical terms must not be judged by present' day standards. When Baer accepted the statement about his "mechanical" opinions as praise, it must be taken as his recognition of the materialistic character of his thought. Baer wanted to assert that his views were opposite to an idealistic "being up in the clouds." His naturalistic approach, based on observations of actually existing phenomena, free from preconceived ideas, must be regarded as a progressive outlook for a naturalist of the first third of the nineteenth century.

In this remark Baer recalled his studies of the history of embryology, in particular the work of Fabricius ab

44. Baer, NACHRICHTEN UBER LEBEN UND SCHRIFTEN, p. 441.

508

Aquapendente. Extremely uncomplimentary about the factual data, 45 Baer stated, "The study of Fabricius was for me an excellent means for recovering from philosophical theories not based on direct observation. 4 ^ Thus, there should be no preconceived explanations, but only accurate observations and conclusions for them."

Baer's "naturalistic" outlook must stand in conflict with the materialistic ideas current in his day, especially in the second half of his career, taking the form of simplified mechanical materialism. His philippics, against naturalists who seek to bring all the vital processes under physico-chemical laws and do not see the qualitative peculiarities of these phenomena, were directed mainly towards the representatives of mechanical materialism. Thus Baer also came out sharply against the other camp — against fideism, coetionism, and anthropomorphism. Here he did not avoid sarcasm and gave a similar kind of opinion to those addressing God, examples of which were mentioned above. What outlook remained? Baer took on the task of creating his own world view. In vain did his biographers promote the idea of a close relation between his study of the direction (Z IELSTREBIGKEIT) of vital phenomena with Aristotle's study of entelechy; in vain they emphasized Baer's sympathy with Spinoza, whose materialistic philosophy they falsely described as pantheism. Baer knew Aristotle well and Spinoza also, but he went his own way as a naturalist, which, of course, could not rise to the heights achieved consequently by materialism.

Namely, this last circumstance was the reason that in the struggle against simplified materialism Baer was sometimes obliged to use ammunition from the arsenal of the fideism and anthropomorphous teleology which he had attacked.

45. "The author used many efforts," Baer wrote, "so that even absurd matters are represented as important and essential . During this he described in detail things which it is impossible to see properly in the egg and also incorrectly described what really can be observed" (NACHRICHTEN, p. 449).

46. The speech was about idealistic natural philosophy, at whose altar Baer gave tribute in his early youth.

509

Attempting to create his own philosophy of nature, giving it a logical basis and providing it with new terminology, Baer mobilized the differences of shades of meaning which had characterized in German the words ZWECK and ZIEL. Rejecting the understanding of purpose (ZWECK) for the organic world,, in whose phenomena he did not discover the presence of a conscious intelligent activity, he strove for the words ZIEL and ZIELSTREBIGKEIT to designate expediency, i.e. adaptive to the building and function of living beings, and in particular their development either individual or historical. The development of the individual which is steadily (ZIELSTREBIG, ZIELMASSIG) producing in each generation all principal signs of the species, was for Baer an especially conclusive proof that the processes of development cannot be directed by accidental actions of the physico-chemical powers.

Baer's frequently repeated assertions that the final end (ZIEL) of development of an individual is the formation of the organism, that in development a steady movement towards this find end (ZIELSTREBIGKEIT) appears, do not have in Baer that outspokenly idealistic opinion expressed by the analogies of vitalists and antidarwinists at the end of the nineteenth and the beginning of the twentieth century. Even using the expression — which is interesting in the idealistic form — that the development of the individual is directed by the idea of the species, Baer apparently had in mind primarily an idea that the direction of ontogeny in each given generation repeats the ontogeny of the previous generation, i.e. that the development of the individual is determined by specific peculiarities which may appear more distinctly in the adult condition. It can be recognized that in Baer's discussions and mainly in his terminology, the knife's edge of difference between ZIEL and ZWECK is so minute that he continuously risked sliding from the meaning of ZIEL into the meaning of ZWECK; undoubtedly this happened in many of his statements. It can be recognized that Baer was insufficiently constant in his struggle against fideism and that some of his expressions are open to deistic and pantheistic interpretations. However, neither these separate idealistic discussions nor the appearance of inconsistency should interest those who want to make for themselves a correct estimation of the views of the great naturalist.

510

Baer's teleological discussions were, as stated, directed against popular materialistic neglect of objectivity which existed expediently (adapt ivity) in the structure and vital activity of organisms. These discussions were, however, inconsequent and sometimes invested in idealistic form because Baer, denying adaptive evolution in the animal and plant world as the result of natural selection, by the. same token passed over the real source of expediency in living nature.

Skepticism toward the idea of evolution, toward Darwinism, led Baer, especially in the last years of his life, to deviate from the materialistic opinions characteristic of the period of scientific activity to which his unfading embryological works are related.

Nevertheless, in relation to Baer, we may cite the man who may correctly be called the greatest thinker of the Russian Academy of Science for a century before Baer — Mikhail Vasilevich Lomonosov: "As to people serving the Republic of Science, I shall not attack them for their ._ errors, but I will try to put into action their good ideas."

47. See "267 Remarks on Physics and Corpuscular Philosophy," 16th Remark, M. V. Lomonosov, SOBR. SOCH., Vol. I (Izd. AN SSR, 1950) .

Chapter 25. Investigations on Invertebrate Embryology - Work of A. Grube, A. D. Nordmann, N. A. Warnek, and A. Krohn

During the first twenty to thirty years of the nineteenth century, embryology remained chiefly the study of the embryonic development of vertebrates; the comparative peculiarities of development of different animals was studied only at the limits of this most studied group. By the end of the twentieth year of that century, i.e. the period of Baer's active work in embryology, the first investigations into the development of invertebrates appeared. Baer himself, as mentioned above, 1 turned his attention to the characteristic peculiarities of development of arthropods, noting in particular that their blastoderms are situated on the abdominal side of the egg and distributed from here in the dorsal direction. Baer was not able to explain the development of arthropods more clearly. Even the investigations of his predecessor Herold, which were limited to the study of the late stages of development of butterflies and spiders, 2 could not give Baer material for well-grounded comparative embryological conclusions.

The aspiration to apply embryological principles to arthropod development was actualized by Baer, first in the study of embryonic layers, reflected in the works of

1. See Chapter 15.

2. J. m. D. Herold, ENTWICKELUNGSGESCHICHTE DER SCHMETTERLINGE ANATOMISCH UND PHYSIOLOGISCH BEARBEITET

(Cassel u. Marburg, 1815), vi + 118 + xxxiv pp.; EXERCITATIONES DE ANIMALIUM VERTEBRIS CARENTIUM IN 0V0 FORMATIONE. DE GENERATIONE ARANEORUM IN 0V0

(Marburg, 1824) , x + 63 pp.

M. H. Rathke. A native of Danzig, Rathke in 1829 arrived in Russia, where he was professor for six years at Dorpat University. Before that, he published many embryo logical works, including a valuable work on the development of crayfish. 3 During his tenure at Dorpat, Rathke visited Moscow and Petersburg and also travelled in the Crimea to investigate the fauna of the Black Sea. On the Black Sea coastline, Rathke collected comparative embryological material which was later used in ON MORPHOLOGY: TRAVEL NOTES FROM TAURIA.4 in this collection, in addition to brief information about the embryonic stage of actinia, there is also an essay on the embryology of the Crimean scorpion and investigations concerning the development of nine species of Crustacea of different orders (copepods, araphipods, decapods, and isopods) . Rathke 1 s work on crayfish development, and also his investigations on the development of other arthropods (124), represent a clear interest in describing the phenomenon of embryonic development in arthropods according to the ideas of Pander and Baer. Rathke spoke of the embryonic disk or blastoderm, of the primary cavity, and of the two embryonic membranes (serous and mucous) into which the blastoderm is divided. The first stages of development, the division of the ovum and the first processes of separation of the rudiments, remained untraced.

It must be borne in mind that a clear presentation about the essence of the processes which take place in the early stages of embryonic development — i.e. first of all the process of division — was not yet established in the first forty years of the last century. Thus, Reichert (125) studied the development of the frog ovum but reached an incorrect conclusion about the structure of the still-undivided ovum, supposing that it consisted of many cells (by cells he meant the round accumulations of the yolk plates) . This point of view was raised by Reichert both in his DIE ENTWICKELUNGSLEBEN IM WIRBELTHIRREICH and in an article published one year before, "On the Process of Division in the Ova of Amphibia, "5

3. H. Rathke, UBER DIE BILDUNG UND ENTWICKELUNG DES FLUSSKREBSES (Leipzig, 1829) , 97 pp.

4. Rathke, ZUR MORPHOLOGIE. REISEBEMERKUNGEN AUS TAURIA (Riga und Leipzig, 1827) , 192 pp.

5. K. B. Reichert, DIE ENTWICKELUNGSLEBEN IM WIRBELTHIERREICH (Berlin, 1840), x + 261 pp.? "Uber den Furchungsprozes der Batrachier," ARCH. ANAT . PHYSIOL. (1841), pp. 523 541.

514

in which he wrote: The process of division of the amphibian ova is nothing more than successively accomplished generic action (GEBURTSACT) of the maternal cells, repeatedly invested in each other.

T. Bischoff, working on the embryology of mammals and publishing in the period from 1842 to 1852 a monograph about the development of man, rabbit, dog and guinea pig, also did not reach a clear understanding of processes of division and did not recognize the spheres resulting from division as cells; since in his opinion, the cell must possess a cavity, but the spheres resulting from division are filled with yolk, the nuclei of the blastoderms were taken by Bischoff as fat droplets.

A. K8 Hiker** went much further in the analysis of the process of ovum division, admitting the direct continuity of the blastoderms and those cells from which the embryo is built in later stages.

In all these cases the discussion was about the forms of development, complicated by the great quantity of yolk in the centrolecithal and telolecithal ova. The nature of the occurrence there of superficial and discoidal division was explained much later, after the introduction of sectioning in embryology.

A more distinct presentation on the phenomena of division was stated by Baer in his work on the development of amphibia, 7 but especially in the work noticed by his contemporaries and later forgotten on the development of the ova of the sea urchin. 8

Certain embryologists of the thirties and the forties nearly approached the correct interpretation of the phenomena of the ovum division. They include KClliker, then Loven,9

6. A. KSlliker, ENTWICKELUNGSGESCHICHTE DER CEPHALOPODEN (Zurich, 1844), 180 pp.

7. See Chapter 21 .

8. See Chapter 23.

9. S. L. Loven, "Bidrag til kannedomen af Molluskenas untveckling," K. VET. AKAD . HANDLINGAR (1839), pp. 227 - 241.

Sars,10 van Beneden,H and Quatrefages-^ and must be mentioned. The first four investigated mollusc development, and the last studied the development of annelids. They presented some stages of ovum division, but did not broach the subject of the internal processes occurring in it nor of the fate of the spheres of division.

A great part of the works of that time concerning the development of invertebrates was illustrated by the study of different types of reproduction, and also by the description of the structure and the transformation of different larval forms which sometimes did not yield to systematic determination and figured under different specific names (126) . The investigations of forms of reproduction became especially popular after Steenstrup showed the wide distribution of the alternation of sexual and asexual generations of many invertebrates; the application of this empirical regularity to groups of animals not investigated before this time constituted the majority of works in the present sphere. The single base for generalization concerning early embryonic development is thought to be the cellular theory formed shortly before this. Using extremely imperfect microscopic techniques, the embryologists of the first half of the nineteenth century posed the question, can the spheres of division be called cells, and are the cells of which the embryo consists the direct descendants of the primary spheres of division? They attempted to trace the fate of those existing in the unfertilized ova "embryonic vesicle" (and "embryonic speck"), i.e. to explain whether these formations disappear after fertilization without a trace or whether they stand in continuous genetic connection with the nucleus (and the nucleolus) of the cells of the embryo. On the foundation of a one-sided and primitive understanding of the cellular theory, fantastic presentations sometimes grew, like the ideas of Reichert, which resurrected the long-buried theory of preformation.

10. M. Sars, "Beitrag zur Entwickelungsgeschichte der Mollusken und Zoophy ten," ARCH. NATURG . , 6 (1840), pp. 196 - 219.

11. P. J. van Beneden et Ch. Windischmann, "Recherches sur l'embryogenie des Limaces," ARCH. ANAT . PHYSIOL. (1841) , pp. 176 - 195.

12. A. de Quatrefages, "Sur l'embryogenie des Annelides," ANN. SC. NAT., 3 Ser. Zool. 8 (1847), pp. 99 - 102.

For the purposeful coordination of the efforts of zoologists studying invertebrate development, the theory of embryonic layers, which still had not become a broad scientific generalization, could not serve. Its correctness was proven only for vertebrates, but the application of the theory of embryonic layers to invertebrates was believed by nearly no one. Rathke's old data concerning crayfish were known. More than a quarter of a century later Zaddach also reported on the embryonic layers of insects, admitting to his descriptions crude morphological mistakes.

The data related to the development of different types of invertebrates were accumulated relatively slowly, because a theoretical conception for which this material could be used did not exist. The study of the types of structure and development of animals, taking its beginning from the opinion of Cuvier and Baer, fell into decay. The formally opposite theory of types, that of Naturphilosophie, the idea of unity of planes, caused little enthusiasm. Only after fifty years, after the appearance of Darwin's theory, did this period of mental stagnation end. Then the naturalists were divided into two camps — the hearty supporters and the violent opponents of the theory of evolution. Practically none of the contemporaries of the great reformer of biological science could keep an olympian calm and sustain neutrality for any length of time.

The investigations preceding the publications of the ORIGIN OF SPECIES played, however, its historical role. Factual material was collected which Darwin and his early followers used. In this period came the important works of the Russian embryologists A. Grube, A. D. Nordmann, N. A. Warnek, and A. Krohn.

To Dorpat University professor A. Grube belonged serious investigation on the development of annelids; he studied the embryonic and partly post -embryonic development of the Proboscidea leeches Clepsine oomplanata and C. biooulata (genus Glossosiphonia, according to the current terminology). 13

Adolf Edward Grube* 4 was born in 1812 in Konigsberg, where he graduated from the university. For thirteen years C1843 - 1865) he was professor of zoology and comparative anatomy in Dorpat University, and to this period of Grube's life are related his most important works in systematics, anatomy, and embryology of the annelids.

Grube's work undoubtedly possesses remarkable significance. Because it was undeservedly forgotten and not mentioned even in the detailed reports and special works on the development of leeches (127), we must dwell here on its content.

In the introduction to his work, Grube turned to memories of his years of study in Konigsberg, where Baer was working. Actually the great embryologist at that time read few lectures, being engrossed in the investigations of development of fish and amphibia. He was helped by Grube's friend, the clever graphic artist Burov, who, by the way, encouraged Grube's attraction to the laboratory, where the latter acquired a taste for embryological investigations. Grube was aware of the difficulty of these observations, but he did not abandon his idea of devoting himself to embryology.

13. A. E. Grube, UNTERSUCHUNGEN UBER DIE ENTWICKLUNG DER ANNELIDEN. I: UNTERSUCHUNGEN UBER DIE ENTWICKLUNG DER CLEPSINEN (Konigsberg, 1844),

ii + 56 pp.

14. The author expresses heartfelt gratitude to the head of the Department of Zoology at the University of Tartu, Professor Kh. Kh. Riikoya, for the photo reprinted here of A. E. Grube.

Shortly after graduation from the university, Grube left for a trip to the Mediterranean seacoast. "Baer's observations on the history of animal development," Grube wrote, "accompanied me on the trip to Italy, and along with the enjoyments of nature and art I continuously sated my interest in this sphere of science" Cp. 1). On the coast Grube zealously collected zoological materials and made dissections, considering these studies important for his future embryological investigations. His attention was attracted mainly to annelids, the study of which became his basic zoological specialty. Only in 1839 did Grube turn to work directly on annelid development, beginning with the study of the very small ova of the Saenuris vaviegata described by Hofmeister. In addition he reported that their development differs in many relations from the corresponding phenomena in medical leeches which had been very superficially described by E. Weber. The following spring, Grube studied the embryology of the leech and confirmed the reality of the formerly discovered differences. Preparing the results of his observations for publication, Grube conscientiously studied the works of the authors whom he considered his predecessors. The work of Filippi on the anatomy and embryology of Proboscidae leeches,! 5 recently published, especially interested him. Grube found that in Filippi' s investigations there was only scanty information about the division of the ovum, as the Italian author saw only "six lobes, situated in one and the same plane around the seventh, situated in the center." To this description he added that these spherical segments disintegrate into smaller spheres (GLOBULI ORGANICI), sharing in the formation of the embryo. Filippi apparently studied the developing ova through the membrane of a cocoon, which can explain the indistinct results of his observations. The first foundation of the embryo Filippi described with an indefinite expression-— cutis (LA CUTE) . He also erroneously considered, that the hatched young is nearly similar to the adult leech and at once is attached to the mother by the help of posterior suckers (in fact they are not present at this time) .

Grube could trace the development of Clepsine in incomparably more detail; his success was aided by the application of concentrated reagents, in particular diluted nitric acid. In the first section of his work, Grube described the structure of the female and male sexual organs, copulation, the act of deposition of eggs, and also the structure of the ova at the time of maturation and directly after deposition.

15. F. de Filippi, LETTERA AL S. DOTT . RUSCONI SOPRA L'ANATOMIA E LO SVILUPPO DELLE CLEPSINE (Pavia, 1839) .

The still-undeposited egg, hung in a special pocket in the oviduct, consists of a fine-grained substance (molecular bodies) and yolk (fatty bodies) ; it is provided with a nucleus (embryonic vesicle) . Before the deposition, the ovum, which is separated from the oviduct and is freely situated in the egg-reservoir, has the same structure; the nucleus already cannot be seen in a beam of light and can be seen only during the crushing of the ovum. Later the embryonic vesicle disappears completely.

The second section of the work was devoted to the description of embryonic development. In the deposited ovum for one hour no change can be seen, and then at its poles the following phenomena can be observed. At the beginning, on one of them, a white spot appears; this increases and turns into a disk with a grey spot in the center (Figure 36, a). Then this grey center increases and a white spot appears in it, and the external white disk is transformed into a ring, which Grube called the polar ring (Figure 36, b) . The field of formation of the polar ring he called the active pole, since according to his observations, it is here at the time of development of the embryo that the most noticeable changes take place. On the opposite inactive pole a white ring appears, but less distinctly delimited. The polar ring ascends over the surface of the ovum in the form of a papilla, so that after its infiltration its condensation can be prepared. Grube considered that the formation of polar rings is the result of the displacement of an internal substance, during which the "molecular bodies" are gathered in the form of rings on the poles.

Following the appearance of polar rings, or, in Grube* s expression, "the process of formation of fissures (DURCHFURCHUNG) or, rather, cleft (ZERKLUFTUNG) . . . . those fissures not only occur on the surface, but penetrate deep into the mass of the yolk, as a simple experiment shows: under careful pressure of the condensed yolk, it disintegrates into as many parts as the segments are delimited by the fissures" (p. 17). The first fissure divides the ovum into two unequal parts [Figure 36, c), so that the polar ring can be divided into halves, or from it a small part is separated, or the fissure occurs in direct proximity from the ring, not touching it completely. The second fissure divides the small segment approximately at a right angle to the first (Figure 36, d), and the third also divides the large segment (Figure 36, e] .

Thus, the ovum passes into the stage of four blastomeres (Grube noted that the large segment in many cases is divided earlier than the smaller one) . Of the four segments formed, one is larger than all the others, and it is divided by a fourth fissure which provides the beginning of the fifth segment. The following division is concerned with this last and takes place not along its length, but transversely, the result of which is that the divided fifth segment forms a region in the form of a polar field in the inactive pole of the ovum (Figure 36, f) . The sixth, seventh and eighth fissures again go from the active pole to the polar field of the inactive pole. After the sixth division the polar ring on the inactive pole usually disappears. Grube did not see more than eight meridional divisions, and said that in leeches the blackberry stage characteristic for many animals is absent; in this stage the meridional divisions are replaced by transverse ones.

At the same time as the division, accomplished by means of fissures, in the ovum of Clepsine the process of separation of the small globules from the large segments of the ovum first described by Grube takes place; these globules Grube called WANDUNGSBALLEN . In his opinion, the wall of the body of the embryo is built from them; "Segments of the yolk" and Wandungsballen are nothing more than the macromeres and micromeres of the terminology of today's embryology. The first small globule, as Grube noted, appears on the active pole after the formation of the first fissure and appears to be situated in this fissure. Judging by time and place of the appearance of this globule, here the discussion does not concern the formation of the micromeres, but the separation of the first polar body. The following small globules, forming on the active pole of the ovum, undoubtedly are micromeres. Grube described their accumulation, ascertaining during this that by the increase of the number of fissures the number of micromeres increases also; however, these phenomena do not stand in an indissoluble connection (Figure 36, e and g) . The formation of micromeres, according to Grube's description, is accompanied by the replacement of substances inside the ovum segments; he described these replacements in detail, alternating the statement of facts about his observations with theoretical conjecture about the forces of attraction, points of their application, and so on.

The micromeres, accumulated on the active pole, do not exhibit equal size; the smaller they are, there are relatively larger molecular substances (protoplasm) anc i smaller fatty globules (yolk) in them. The smallest consist only of protoplasm and a round transparent nuclear body. These micromeres, according to Grube, never arise from macromeres; therefore, he wrote, "I must conclude that the small globules originate from those large globules already present on the pole which earlier separated from segments of yolk" (p. 22). The accumulation of micromeres forms a plate in the form of an isosceles triangle, without sharp limits passing into the other surface of the ovum. This plate, which Grube called the embryonic field, is so situated that the summit of the triangle is turned toward the active pole and corresponds to the cephalic part of the future embryo.

It consists of "mosaic pieces" which arise as a result of the multiplication of micromeres; in addition, these pieces are smallest when they are nearest to the cephalic end. In the stage described, not only the anterior and posterior ends of the embryo, but also its upper and lower sides, as the surface of the embryo, on which the embryonic fluid is situated, correspond to its abdominal side. Using the descriptive phrase "mosaic pieces", Grube resolved consciously to avoid using the term cell, not being sure that it inherits its own features, which are characteristic of typical, in particular plant, cells.

The anterior end of the embryonic field quickly expands (Figure 36, c) , and by forming two summits it produces S-shaped curved shafts (Figure 36, j), which Grube called the abdominal shafts. This name is well-founded, because these shafts, appearing in the field of the active hemisphere of the ovum, i.e. the future dorsal side of the embryo, are displaced towards its ventral side, where they later accrete into a single ventral embryonic region. The ventral shafts, according to Grube, on the ventral side of the leech embryo play the same role which the dorsal shafts play in the vertebrate embryos, because from them the wall of the body, in particular its muscles, is formed. The ventral shafts are composed of extremely small, closely adjacent other globules. At the posterior end of the embryonic field remain large globules which form part of its molecular (protoplasmic) content; three of these terminal globules usually are present on each side (Figure 36, k) . The internal part of the yolk globule (the divided ovum) constitutes a mass containing little protoplasm. This rich yolk mass is used mainly for building organs which are present in the abdominal cavity, in particular the intestinal canal; above it a layer grows, composed from a molecular mass which takes its origin from the ventral shafts.

Figure 36. The development of Clepsine (by Grube) .

a — fertilized ovum, b— ovum on which the white disk with grey ring appeared, c— first fissure; the white disk is present near it. d — yolk globule, divided into four parts, e— yolk globule, divided by six transverse fissures; the polar field increases as the surrounded globular segments decrease in size due to the loss of albumen (molecular) mass used for the formation of WANDUNGSBALLEN on the active pole, f — -the same stage, globules of division from the lower side; on the inactive pole the polar field is seen, i.e. the surface of the seventh segment, separated from the other round fissures, g — somewhat later stage, view from, above; the number of WANDUNGSBALLEN increasing, they then form a small disk which can be regarded as a rudiment (KEIM). h — WANDUNGSBALLEN increase in number and occupy a great area, forming the embryonic field, i — the view of the abdominal shaft from behind; they move so far apart that they envelop the yolk globule by a ring . j— the abdominal shaft from the side; on the posterior end of each, three whitish globules are present, k — the abdominal shafts unite together.

The rudiment of the neural cord appears in the form of two white stripes, joined to the external side by the recently formed embryonic stripes. After their closure on the ventral sides, the halves of the paired rudiment of the nervous system are united.

In this period the surface of the embryonic body is already covered with epithelium, composed of flat cells of different sizes and forms. At the same time in the body cavity dissepiments are situated, their number gradually increasing.

In the third part of Grube f s work he included changes occurring after the hatching of Clepsine from the egg membrane. Contrary to Filippi, Grube found very essential differences between the just-hatched leech and the formed worms. In the short, cylindrical little worm hatching from the egg, there are still no posterior sucking discs, no eyes, no blood vessels, and the formation of the dissepiments is also unfinished. As the young larvae are also immediately fixed by the anterior end, Grube assumed the presence of the rudiment of the anterior sucker with longitudinal and circular muscles. Within one day after hatching this sucker is clearly noticeable in the form of a convex ring; after two days this ring elongates, as Grube thought, under the effect of the heaviness of the body of the leech hanging on it. Inside the elongated ring a canal appears representing, according to Grube, the rudiment of the sheath of the still unformed proboscis. The wall of the intestinal canal, or yolk sac, consists at this time of large cells. Later, by means of a circular twist of the most anterior part of the body, the caudal disc develops and the proboscis is formed, which the larva can let out and pull in. The digestive canal is formed in this way. On the intestinal canal extensions appear, and in addition to this, it is divided into three parts. The anterior and posterior parts are significantly thinner than the middle one which composes the future stomach. In the last the more enlarged lateral pouches appear. Later on the eyes develop; at first they have the form of circular red spots. The vascular system develops, and, on the dorsal side of the body, the pulsating heart first becomes noticeable.

Grube finished the description of his observations with the following words: "The development considered here is probably spread extensively in the class ANNULATA. This is established on the basis of detailed investigations on many representatives of Naidae and Lumbricinae namely in Saenuris variegata Hoffm., Euaxes acutirostris Gr. and Lwnbvioulus variegatus Gr., and if it can be judged by an analogy with the adult animals, it will be also correct for the genus Lumbricus, and also for many sea worms" Cp. 45). With this, Grube carefully observed that discussion of analogy without special investigations can lead to erroneous conclusions.

A discussion of Grube' s work leads to the conclusion that he promoted the study of embryology of the annulated worms (annelids) and discovered phenomena the detailed study of which was done significantly later. His most important achievement in terms of recent embryology can be summarized in the following way:

1. Grube established that in the eggs of Proboscidea leeches there are polar plasmas; especially conspicuous are protoplasmic rings on the animal pole.

2. He recognized the complete, unequal division of the ovum of Proboscidea leeches, during which the animal polar plasma can go in one of the blastomeres of the four-celled stage.

3. Grube clearly saw how in the stage of the four blastomeres, from the animal side, very small globules of division began to separate; i.e. he established the fact of the formation of micromeres, which are composed mainly of protoplasm, and macromeres, which are rich in yolk.

4. Later he established that the number of micromeres increased either by separation from macromeres, or by means of multiplication of the early formed micromeres.

5. By Grube' s observations, the "rudiment" which is formed on the animal pole, owing to the multiplication of micromeres, spreads over the surface of the ovum, as a result of which the macromeres appear inside the embryo. This phenomenon very nearly resembles epibolic gastrulation.

6. At the end, Grube described the embryonic stripes coming out from three pairs of terminal cells; i.e. he discovered in the annulated worms the phenomenon of teloblastic development.

7. The embryonic stripes, in Grube' s observations, are displaced towards each other and are united on the ventral side. From the material of the embryonic stripes ("the abdominal shafts") the wall of the worm's bodytegmens, muscles, and nervous system is formed.

Grube 's excellent work was forgotten, and superiority in the study of the embryology of annulated worms, in particular the leeches, was accorded to Rathke, whose work was published eighteen years later. Rathke 's work without doubt has merit, but also has many defects, so that it can be seen as a step backwards in comparison with the work of Grube. Thus in the maxillary leech Nephelis vulgaris Rathke clearly saw the formation of micromeres, which in Clepsine complanata he did not see, and instead of the micromeres only granularity is illustrated in his drawing in the animal parts of the blastomeres. At a later stage it is shown as if the unlacing of the micromeres has begun, but he did not see whether this led them to division. Together with this, Rathke reproached Grube for seeking the source of micromeres CWANDUNGSBALLEN) in the depths of the globules of the division, while Rathke himself in general did not see their separation. According to his description, a number of hillocks on the animal pole of the divided ovum directly turned into a thickening which is the rudiment of the embryonic stripes. The embryonic stripes of Nephelzs are illustrated very schematically by Rathke; he did not observe the characteristic cellular rows in these stripes, neither did he recognize the connection between the only three teloblasts illustrated in his drawing which are situated as if they lie at the extreme ends opposite to the embryonic stripes and the middle one as if it lies between these ends. Rathke also represented the embryonic stripes of Clepsine less distinctly than Grube.

All this is mentioned not to underestimate the significance of Rathke ! s investigations, but only to drawattention to the more perfect work, in many aspects, of Grube, to call to mind its priority and to show the importance of his work in the history of Russian and world embryology.

In the 1830' s and 1840' s, the development of invertebrates also interested A. D. Nordmann (1803 - 1866). Aleksandr Davidovich Nordmann was the son of a Russian officer born in Finland. In 1821 he entered the university in Abo, and after graduation he worked for some years in Berlin with Rudolphi and Ehrenberg. During his stay in Germany he accompanied Oken, Tiedemann, and Chamisso on a trip for the study of sea fauna. In Berlin Nordmann published his first work, MICROGRAPHICAL INFORMATION, dedicated to the structure and taxonomy of parasitic worms (describing many new forms, in particular "spainika" - Diplozoon paradoxwi) , and also the structure and development of parasitic copepods.16 In 1832 Nordmann was invited to join the department of zoology and botany of Lyceum Rishel in Odessa, and in the following year he took the post of director of Odessa Botanic Garden C128) . In 1833 Nordmann together with Rathke, S. S. Kutorgaya and Steven travelled to the Crimea. In the following years he travelled much in the south of Russia; in particular, he led excursions in the Crimea of students of the Odessa Lyceum. When he was sent with a scientific mission to Paris, Nordmann visited with Milne-Edwards the coast of Normandy. In 1849 Nordmann came to Helsingfors University, where from 1852 to the end of his life he headed the department of zoology. During the period of his scientific activity, Nordmann published fifty-seven works in Russian, Latin, German, French and Swedish on anatomy, embryology, taxonomy and zoography of different groups of vertebrates (mammals, birds, fish) and invertebrates (insects, spiders, crustaceans and worms, mainly the parasitic molluscs, bryozoans and Coelenteratae) ; he also studied botany and paleontology.

16. A. v. Nordmann, MIKROGRAPHISCHE BEITRAGE ZUR NATURGESCHICHTE DER WIRBELLOSEN THIERE (Berlin, 1832), Vol. I, viii + 118 pp., 1: UBER BINNENWURMER IM AUGE HOHERER THIERE; 2: BESCHREIBUNG EINIGER NEUEN HELMINTHE. vol. II, xviii + 150 pp., 1: BESCHREIBUNG EINIGER NEUEN PARASITICHEN ENTOMOSTRACEEN; 2: ERSTER BEITRAG ZUR NATURGESCHICHTE DER LERNAEN.

In the previously mentioned MICROGRAPHICAL INFORMATION, the results of Nordmann ! s observations on the development of parasitic copepoda Aahtheres peroanon appear, and the larval stages of other related forms (Ergasilus Sieboldi Nordm. , Traoheliastes polycolpus Nordm. and Lernaeoaera cyprinacea) are described. These investigations met the need to explain the systematic situation of parasites, which at that time were related either to molluscs or to the annulated worms, or even to coelenterates. If the relationship of some representatives of the mentioned groups Cf° r example, Caligus) to crustaceans was to some extent only probable, then these forms, such as Lemaeocera , which in the adult condition are completely unlike arthropods, remained in their systematic relations mysterious.

The embryonic development of Aahtheres was described by Nordmann rather incompletely. "On the upper surface of the yolk," he wrote, "is found at first a more transparent region, an4 a granular part of the yolk, having the significance of a rudiment (KEIM) , turned into round or spherical forms from which the more peripheral give material for the formation of the rudiment membrane (KEIMHAUT) ... The latter completely envelops the yolk and... forms later on the wall of the body of the embryo (p. 78). After referring to the separation of the head and the appearance of the rudiments of the extremities, Nordmann turned to the characteristics of the nauplius larva, whose structure becomes complicated after moulting.

Its central point was the description of the larval stage of Lemaeooera oyprinaoea . The adult animals of this genus were already known to Linnaeus; they are characterized by a sacculated unopened body, deprived of extremities and organs of sensations (Figure 37, A). "If naturalists," Nordmann wrote, "are astonished at the structure of the body of the mature animal of this kind, their astonishment will be more natural when an opportunity arises for them to observe the young animals. It can hardly be imagined that there is anything more striking than an offspring having absolutely nothing in common with its parent. Before my eyes the egg receptacle in the mature animal was ruptured, and the embryos set free. I saw young animals exactly the same as I represent them in the drawing (Figure 37, B) ; they have extremities, antennae, and even bright red eyes" (128).

Nordmann 1 s observations met, according to him, decided distrust from Berlin zoologists to whom he demonstrated the nauplius larvae of Lemaeooera oyprinaoea. Later the significance of this discovery was universally recognized (129) .

After some years Nordmann published a small embryological work concerning the Black Sea bryozoan Tenchca zosterioola A 7 In one zooid Nordmann found from four to seven eggs and saw the penetration of the spermatozoids in the female cells through an opening in their base. Later he saw the embryos hatched from the eggs swimming by means of cilia and finally settling in the seaweed Zostera. "As far as it is possible," Nordmann wrote, "I observed the transformation of the young animals and the development of polyps from them." Greater significance was possessed, however, by other embryological work of Nordmann' s on the development of molluscs.

17. A. v. Nordmann, "Recherches microscopiques sur l'anatomie et le developpement du Tendra zosterioola, espece de polype de la section des Bryozoaires , " ANN. SC . NAT. ZOOL., 11 (1838), pp. 185 - 191.

Figure 37. Lernaeooera cyprinacea (A) and its larva (B) (by Nordmann) .

The molluscs, especially the gastropods and lamellibranchs, are considered easily available material for the study of development processes; therefore they early attracted the attention of embryologists . The division of the ova of the gastropod molluscs is described in the investigations of Van Beneden and Windischmann, and the division of the ova of the lamellibranchs — in the work of Loven. In the ova of Modiolaria marmorata {Mytilus aisoors) Loven observed a maturation division and described it, as a process of ejection of nucleolus (embryonic spot) . The important result of his work was the establishment of the fact that during the division of the ovum of Modiolaria, the separation in the vegetative hemisphere of non-nucleated lobes takes place which soon merges with one of the blastomeres. This phenomenon is repeated many times during the time of the following divisions. Loven saw clearly the process of division itself, i.e. the deviation of the ovum into separate blastomeres, but he did not trace the changes in the nuclei, the equal and mutual distribution of blastomeres .

The separation of polar bodies in the ovum of the grey slug is sufficiently clearly described in the above-mentioned works of Van Beneden and Windischmann, although the division following the separation of the polar bodies was inaccurately described by them; they spoke about the formation of elevations on the surface of the yolk, divided by fissures. As a result of this the entire surface of the ovum becomes at the end as if embossed (BOSSELE) and resembles a raspberry, The Belgian authors did not connect the formation of "the yolk cells" with the appearance of the cuts on the surface of the yolk; according to their concept, the yolk cells originate under the superficial layer of the yolk. The drawings illustrating their work show round bulges on the surface of the developing ovum, and not its division as a whole into separate blastomeres. The internal processes in the divided ovum and blastomeres are neither described nor illustrated in the drawings. Erroneous ideas of the processes of division in the gastropodan molluscs were retained in the work of 0. Schmidt appearing ten years later. 18 "The description of the ovum and the processes of division inside it up to the formation of the embryo," Schmidt wrote, "was given so completely by van Beneden and Windischmann that I cannot add anything to it" (p. 278).

18. O. Schmidt, "Uber Entwickelung von Limax agvestis , " ARCH ANAT., PHYSIOL. (1851), pp. 278 - 290 .

The subject of Nordmann's above mentioned work on the development of the gastropodan molluscs was the nudibranchiate mollusc Tergipes Edwardsii . The description of the phenomena of its embryonic development constitutes part of the extensive monograph, 19 beginning with the presentation of anatomical data. Nordmann described in detail the development of the ovum in the ovary (5 28 - 31), characterized the yolk elements of the ovum (§ 32) , the structure of the egg ready for oviposition (5 33) and its membranes (5 34) . The process of division {§ 39) of the ovum of Tergipes was described by Nordmann as the following: the first fissure of division can take place in different directions and divide the ovum either into equal, or into very unequal parts. The fissure dividing the ovum into four globules of division takes place at right angles to the first fissure, after which the ovum is divided into eight globules, and so on. The generally uneven character of division is noted in the following expression. "Although the tendency to even progressive division cannot be disputed, it also shows that the yolk, especially up to its acquisition of the mulberry form, appears to divide very unevenly" (p. 573) (Figure 38, a-g) . Nordmann noted especially that the fissures cut all the mass of the yolk, i.e. that the division was complete.

19. Nordmann, "Versuch einer Natur- und Entwickelungsgeschichte des Tergipes E 'dwards ii , " MEM . , pres . a l'Acad. Sc. St.-Petersb. par divers savants, 4 (1845) , pp. 495 - 602. A brief translation of this work in French was published by K. Fogt ("Essai d'une monographie du Tergipes Edwardsii," ANN. SC. NAT., 3, ser. Zool., 5 (1846), pp. 109 - 160).

All the course of development of Tergipes Nordmann summarized in the following statements:

1 . The chorion extend to one-fifth the diameter of the ovum and becomes oval . 2 . At this time a light fluid, similar to albumin, discharges from the ovum. 3. The yolk loses its spherical form, its mass loosens, and the contours become wrinkled. 4. The embryonic vesicle and the embryonic spot disappear. 5. The upper layers of the yolk lose their reddish coloration. 6. In too many cases separate yolk cells are separated from the other mass of the yolk and give origin to the parasitic creatures. 20

7 . The ovum is divided by a fissure into two globules .

8. The division process continues regularly.

9. The yolk acquires the form of a mulberry.

10. A bubble of air leaves the yolk (?) . 11. The surface of the yolk becomes granular. 12. First establishment of the embryo. The yolk acquires an elongated form, and then the form of a roughly outlined triangle. 13. The distinct appearance of the animal system and the cutaneous system. The configuration of the embryo. 14. Twisting of the anterior part of the embryo is noted (future organs of movement) . 15. On the wide anterior area folds appear, from which two lateral round growths are gradually formed. The growths are transformed into lobes and between them a third growth, the foot, appears. 17. Beginning of the formation of mantle and concha. 18. On the lobes the cilia grow. 19. The first movement of the embryo. On the foot the vibrating cilia appear. 21. The lobes of the sail become disc-shaped. The rotatory movement of the embryo. 22. Cells sharing in the formation of mantle are dissolved and disappear. 23. The concha significantly enlarges. 24. The isolated cellular rows indicate the formation of the attached muscles .

25. The formation of the internal organs, among which the intestine is distinctly differentiated.

26 . The liver and other glandular bodies are clearly seen. The anus and ganglia.

27. The cells forming the attaching muscles disappear. 28. Deposition of the pigment in the eyes . 29 . Between the chorion and the embryo the astonishing parasites appear to rush out. 30. The complete formation of the embryo larva; the roof of the shell opens and closes. 31. The extension of the chorion. 32. The presence of the young in the common ovum chamber. 33. The larva cuts the chorion. 34. Hatching, (pp. 565 - 567)

20. Nordmann gave this parasite the name Cosmella hydrachnoides and suggested the possibility of its origin from particles of the yolk of Terg-ipes.

Figure 38. The development of Tergipes Edwardsii (by

Nordmann) a-g — division of the ovum; h — larva,

,36

From the above it can be seen that Nordmann's main attention was to the relatively late stages of embryonic development, while he investigated the process of division of Tergipes only extremely incompletely.

The brief discussion of the works of van Beneden, Loven and Nordmann on the embryology of molluscs demonstrated the level of knowledge in this sphere at that time. When the development of molluscs was studied by the Russian embryologist N. A. Warnek, his work can be unconditionally called classical (131). Warnek's scientific activity, unfortunately, was brief and was cut short by external circumstances,

Nikolai Aleksandrovich Warnek was born in 1821. When he was eighteen years old he entered the faculty of law at Petersburg University, but in the same year he transferred to a department of the faculty of philosophy. During his years of study, Warnek received in 1843 the gold medal for his "Process of Moulting of External Tegmens and Formation of Millstone in the Ordinary River Crayfish." In 1846 he graduated from the university with a candidate's degree, and for three years he taught botany and zoology in Gorn Institute. Warnek received his master of science degree for his work on the structure and function of the crayfish liver^l and in 1849 he started reading lectures to naturalists and medical men in comparative anatomy and physiology in Moscow University, first as junior scientific assistant and then as extraordinary professor (from 1852) . In 1848 Warnek wrote the vast work "On the Formation and the Development of the Embryo in the Gastropodan Molluscs," which was published two years later in the BULLETIN OF THE MOSCOW SOCIETY OF NATURALISTS; 22 a summary of this work was published abroad under

21. N. A. Warnek, "On the Liver of River Crayfish in Anatomical and Physiological Relations" (SPb., 1847), 40 pp.

22. warnek, "Ober die Bildung und Entwickelung des Embryos bei Gasteropoden," BULL. SOC . NATUR . MOSCOW, 23

(1850) , pp. 90 - 194.

the title "On the Process of Division and Structure of the Ovum in Gastropods. "23

In 1860 Warnek retired and departed to Tver; where for three years he was director of a secondary school, and then director of the schools of Tver Province.

Until recently it was thought that Warnek 's scientific and literary activity ended in 1863 and that in 1867 he died. From recent work by T. P. Platovaya 2 ^ it is now known that in 1880 and 1881 Warnek read a report to the Moscow Society of Naturalists on the biology of agricultural pests, and in 1884 a report on the microscopic structure of the fish ovum and on the morphology and taxonomy of fish. The exact date of his death remains unknown.

Concerning his retirement from Moscow University evidence has been kept which is probably not completely objective and in any case explains only incompletely the cause of his retirement from teaching and from scientific work.

In the multi-volume apologetical biography of the reactionary historian Pogodin, its author N. Barsukov25 reminisced about I. A. Mitropolsky, who was in 1850 a student in the Faculty of Medicine in Moscow University. According to Mitropolsky, when Warnek was reading zoology and comparative anatomy he was noted for an extremely scornful nature; due to this he was disliked by the students and medical men. One of Warnek 's clashes with the students, Mitropolsky reported, ended in a noisy scandal, in which both students and medical men participated. In order to confirm to the reader the ultimate rightness of the students, Mitropolsky declared that "the students could endure the tricks of the professor only if his lectures gave them anything useful. But they got nothing from them."

23. Warnek, "Uber den Furchungsprozess und die Struktur des Eies der Gasteropoden," FRORIEP ' S TAGESBERICHT , No. 280 (1851) , pp. 43 - 44.

24. See (131) .

25. N. Barsukov, ZHIZN'I TRUDY M. P. POGODINA (Life and Works of M. P. Pogodin), Vol. 16 (1902), pp. 116 - 117

Another aspect of this incident is mentioned in the reminiscences of L. V. Lebedinsky, which were published in VOICE OF THE PAST in 1912.26 Lebedinsky characterized Warnek as talented, but very proud and sharp in his treatment of people, who "excited against himself the students and medical men by his tactless relations with them and an unusual strictness during examinations." Handbooks in Russian in zoology and comparative anatomy were absent at that time, and Warnek suggested foreign books, which the students, due to their ignorance of the languages, found difficult to use. He did not read a systematic course, but selected works of his own, which he considered more important and interesting. In answer to the protests of students on this occasion Warnek declared that "the students of a university are not secondary schoolboys, they must work independently. The professor in his lectures has only to point out a direction and a method by which the students must carry out their work." The dissatisfaction of the students and medical men was expressed in the organization of meetings in which the students of other faculties shared, students of law and philologists who did not attend the lectures of Warnek and could not judge their effects and defects. In these meetings it was decided to criticize the professor, and then oblige him to leave the department. Only some of the students and medical men, Lebedinsky continued, strongly defended the professor. "They said that Warnek was regarded differently and they loved him for his talented presentation of the subject." The planned obstruction was nonetheless carried out, mainly by students of other faculties who shared in the action, especially those of the faculty of law. This produced on Warnek a stunning effect. "Warnek went into an adjacent room," Lebedinsky wrote, "where he fainted away; it is even said that blood gushed from his throat." Soon after this incident Warnek retired, insisting on it despite intensive persuasion.

26. UZ ZHIZNI MOSKOVSKOGO UNIVERSITETA. VARNEKOVSKAYA ISTORIYA. "GOLOS MINUVSHEGO" (From the life of Moscow University. Warnek' s History. "Voice of the Past") (Otd. ottisk, pp. 210 - 218). For this source, as well as for the answer in HERZENOVSKY "K0L0K0LE" (see [132]), the author expresses deep gratitude to V. V. Sorokin .

Already this comparison of evidence shows the impossibility of placing complete responsibility on Warnek himself for what occurred. The objective evidence of Lebedinsky about Warnek f s talented lectures to the students and medical men and their good relation to him unmasks the tendentious assertion of Mitropolsky that Warnek' s lectures gave nothing to the students. The impression one has of Warnek is of a serious, exacting professor who loved his subject and taught it on a high level. Certain students and medical men understood his efforts and valued his services to them, while the majority of students were interested in the applied questions and not in understanding Warnek' s theoretical views, and saw him only as a strict examiner who shamed them, in addition to his ridiculing of their ignorance.

In all this sad "history of Warnek" there is still one significant side which can be read between the following lines in Lebedinsky 's memoirs: "Even among the professors there were people who sympathized with the students, the professor of theology Sergievsky among them. This handsome, somewhat fanciful, young orator was sometimes present in the department. He unnoticeably and cleverly approached the evils of the day, said a few words hinting at an excellent understanding of the students, and was zealously rewarded with applause. In the time of the aforementioned event, one of his lectures, which was full of these hints, ended with the following significant words: 'Yes, this darkness does not triumph over the world!"'

It is logical to ask why Warnek was not pleasing to the professor of theology. What world of darkness and damage spreading from Warnek 's department was frightening to Sergievsky? To answer this question is not difficult. Warnek was a convinced materialist, as is easy to ascertain from a study of his basic work. It is improbable that in his lectures Warnek did not touch upon questions of ideology, which, of course, was used against him by Sergievsky, who considered it his responsibility to protect the world of "religion" from the "darkness" of the natural-scientific materialism. Sergievsky's Jesuitical activity made the best use of the dissatisfaction of the protesting group of students, who played a role obviously of considerable importance in the organization of the obstruction, which took place with the obvious support of the administration of the university, usually so vigilant when the matter is concerned with student disturbances (132) .

The fault, or rather misfortune, of Warnek was his sharp and derisive character, his inability to adapt himself to his surroundings. Warnek did not want to reconcile himself with the manifestations of ignorance, even if its carriers were respectable scientists. This can be witnessed by Warnek 's review of a scholarly book by A. Bogdanov. 27 This review shows great and extensive knowledge and unquestionable educational talent of the reviewer and his understanding of the problem of the teaching of natural sciences. In addition, the review is written in an overly particular and caustic tone; Warnek did not let pass any mistake, any slip of the tongue, or any lame expression from the author of the book. It is easy to imagine what reaction Warnek' s article could produce in Bogdanov. If Warnek behaved similarly in the professional milieu of Moscow University, and used to deride the lectures of his colleagues, then he undoubtedly provoked against himself not only a certain group of students, but also some professors.

Valuable evidence of Warnek 's high character as a lecturer and scientific worker is contained in the words of I. M. Sechenov : 28

Junior Scientific Assistant Warnek taught us zoology. He read simply and clearly, dwelling mainly on general signs applied in zoology departments, and the description of protozoa was prefaced by a long treatise on the cell in general. This last study was built, however, on unprepared ground. Moscow still did not think much at that time of the microscope; among Warnek' s students it was not used successfully, and in mockery they nicknamed him "Cellular."

27. Warnek, "Zoologiya i zoologicheskaya khrestomatiya v obieme srednykh uchebnykh zavedenii , " Author Anatolii Bogdanov, OTD. PERVY ZH. MNP, ch. 118 (1863), pp. 47 - 73.

28. I. M. Sechenov, AVTOBIOGRAFICHESKIE ZAPISKI (Izd. AN SSSR, 1945) , 176 pp.

In a footnote Sechenov added: "Too late, I have learned that Warnek and the famous botanist Tsenkovsky were among the first Russian biologists who worked at that time with the microscope."

On Warnek' s socio-political opinions there is no information. His statement against Eogdanov's book, based on the principles of Darwin's evolutionary study, was published in a government journal; objectively, it could have played a reactionary role. The mutual relations of Warnek with the students creates the suspicion of the possibility that the rising conflict was of a political nature. Concerning Warnek 's "political orientation," it can be seen that he was later assigned responsible posts in the Department of Education. A search of the archival material may throw light on this subject.

For a characterization of Warnek' s scientific work and world view, it is necessary to gain acquaintance with the contents of his basic work, "On the Formation and Development of the F:mbryo in the Gastropodan Molluscs. "^ As an epigraph to this work Warnek selected the words of Reii: "The phenomena of individual life are the necessary result of formation and merging." This idea, as can be seen from the final chapter of this work, Warnek interpreted materialistically. Warnek himself also considered that only in the definite mixing of substances in definite spatial position [form) can the solution of vital phenomena be sought. Science, in his opinion, is not in need of additional idealistic assumptions.

As it is seen from the introduction of his work, Warnek considered his principal task to be the explanation of how the yolk, i.e. ^substances of the ovum, are transformed into tissue of the embryo and what conditions this transformation. The solution to this question, in Warnek' s opinion, is possible only through a thorough investigation of the processes of development, and that is why he also outlined the following vast program. First of all, Warnek suggested, it is necessary to study the reproduction of molluscs, either hermaphrodites or separate sexes. For this aim the following must be studied: 1) structure of male and female sexual organs; 2) origin of

29. See footnote 22 of this chapter

embryo, i.e. development of yolk (ovum) and semen; 3) processes occurring during copulation, i.e. the influence of sperm upon the yolk, and finally 4) formation of the additional parts of the ovum — albumin, membranes and ovum cocoons .

Only after this it is possible to begin the study of embryonic development, which Warnek divided into two periods. The first period includes the development of the fertilized ovum, i.e. the process of division and preparation of the development of organs, and the second, the period of development of all systems of organs of the developing animal.

In his investigations Warnek proceeded from the following situations established by the embryologists: 1) for the transformation of yolk into an embryo fertilization is absolutely necessary; 2) this last consists of the material influence of semen on the yolk; 3) this influence takes place only in an infinitely small space, therefore the spermatozoa of the semen must come in direct contact with the mass of yolk; 4) the result of fertilization is the formation of the elementary organs of the embryo (cells); 5] the cells acquire different forms, grouped in complicated organs of the embryo, and thus form its body.

Warnek expressed regret that embryologists could not completely solve the following important questions related to the development of animals: 1) how the yolk, i.e. substance of the ovum is transformed into tissue of the embryo; 2) how its transformation at the time of development occurs; 3) in what does the secret influence of the semen on the yolk consist.

The first question Warnek considered to be solvable, and he expressed the hope that in a short while the other two questions would also be explained.

The solution of the principal questions of embryology, in Warnek' s opinion, could take place on the basis of the following presentations:

The cause of the phenomena conditioning the beginning and the subsequent development of the embryo is ordinarily attributed to the vital power, which absolutely clearly shows that the beginning of life must be sought in the formation of the ovum in the ovary, and the beginning of its development in fertilization, namely in the influence of semen on the yolk. And, of course, the essence of the powers which condition all phenomena of nature remains unknown. If all this can reduce the different phenomena to one cause, this will make a great step toward the goal we have established, (pp. 94 - 95)

During the last four years, aspiration to a solution of the aforementioned general questions was my dearest hope. Devoting myself year after year to the study of the formation, development, and functions of cells, I have stuck to the idea that elucidation of the ideas of development and activity of the cells is the only way to select from the labyrinth of recent presentations about the organic world. The explanation of the causes of the vital activity in the cells leads to a clear presentation about life in general and about causes directing it throughout the organic world, (p. 95)

The following work of Warnek represents the first part of investigations of his planned program; it is concerned with ovum structure and processes of its division in the gastropodan molluscs.

Warnek began with the description of the form of oviposition of the different fresh-water snails; he detailed the periods of oviposition in the region of Petersburg and the structure of gelatinous mass surrounding the ovum. Later he described the structure of the laid ova, especially in the species used in this work: Lymnaeus stagnalis and the slug Limax agrestis . Transferring to the principal part of the work, throwing light on the study of division, Warnek paused at the characteristics of the yolk granules filling the fertilized ovum. Among these granules Warnek saw a light spot which was not delimited from the yolk membrane and was always situated in the center of the ovum. All the process of division of the ova of the molluscs which he studied Warnek divided into stages, described in succession.

FIRST STAGE: For this stage, characteristic phenomena are taking place in the above mentioned light spot, which, in Warnek's words, occupies the place of the rudimentary (embryonic) vesicle. This spot is in the beginning completely round (Figure 39, 3), then becomes elongated and subsequently takes the form of a biscuit and the shape of a figure eight (Figure 39, 4 and 5). After that when the spot (i.e. nucleus) is twisted by the means just described, it comes nearer to a certain region of the periphery of the yolk (ovum) . The end of the spot which is turned to the surface of the yolk widens, and it acquires the form of a blunt rounded cone, in addition between the outer area of this cone and the membrane of the yolk a transparent crescent-shaped region appears (Figure 39, 7) . From this crescent-shaped region two small vesicles become separated, which, being isolated from the ovum, remain near it throughout the following development. The place of deviation of these vesicles becomes the center of formation of fissures, later dividing the yolk into two, then into four parts.

The separation of the vesicles Warnek described as follows: on the external surface of the crescent-shaped region a small elevation appears under the yolk membrane. It gradually enlarges, acquiring the form of a spherical segment, a hemisphere, then a complete globule, which is set on a sufficiently thick stalk. Then this stalk becomes unlaced, and the globule becomes free (Figure 39, 9). After the formation of one vesicle the second one appears exactly as the first (Figure 39, 9 and 10). Thus, in Warnek's observations, the crescent-shaped region separates the forming vesicles from the light spot (i.e. from both nuclei of the ovum) . He concluded that the nucleus does not share in the formation, at least, of the external vesicles. He made this erroneous conclusion because the intravital observations which Warnek used did not suggest tracing the processes taking place in the nucleus. From this came the further erroneous claim that the separating vesicles could not be regarded as the vesicles of Purkinje or its remnants. In accordance with this assertion Warnek refused to recognize for the vesicles separated from the ovum that important role claimed for them by many authors, and he objected to the name "directing vesicle" {vesioula directrix') . Warnek did not like this name as it returned embryologists to the time when they believed in an Archean spirit directing vital phenomena.

The presence of vesicles where the formation of fissures of division begins did not prove, in Warnek's opinion, that the topographical position of the fissures was determined by the vesicles. Preferably, as he thought, the matter was the contrary: the vesicles are separated where the center of division is present. In later stages of division many fissures appear without preliminary separation of the vesicles

After the separation of both vesicles the transparent crescent-shaped region also disappears. In the ova of the slug there appear two nuclei distinctly separated from each other. At this time the nuclei each acquire distinct contour and a large nucleolus.

THE SECOND STAGE begins with the loss of the membranes of the nuclei and their merging into one common mass. This mass acquires an extended form, situated on the longitudinal diameter of the yolk, i.e. at right angle to the position which is characteristic for the first stage (Figure 40, 11) . Then the nucleus becomes biscuit-shaped (Figure 40, 12) and at the same time the division of the yolk begins. In the last description Warnek used topographical terms, and their significance is explained in the literal remark. The transverse diameter he called the diameter; passing through the vesicles from the yolk at right angle to it the longitudinal diameter is situated. The terminal points of these diameters he called poles: the dorsal pole in the place where the external vesicles were present; the ventral pole situated against the dorsal one; the poles of the longitudinal diameter designated as right and left.

The division of the yolk is preceded by a thickening of the dorsal pole, in its field; then a fissure in the form of a cut appears. Due to its deepening the ovum becomes in form more like the kidney (Figure 40, 13) . The direction of the fissure does not coincide with the transverse diameter; it is inclined to it at a 45-degree angle. The light spot decreases and becomes less noticeable even in the ova of the slug, and in (Lymnaeus stagnali-s) it is not seen in the majority of cases from the very beginning of the division.

Figure 39 . Warnek ' s drawings for his work on the development of gastropodan molluscs (development of Lymnaeus stagnalis)

3-5 — the division of the light spot in the fertilized ovum;

7 — at the external area, light spot coming near the surface; a light crescent-shaped formation appears; the beginning of the formation of elevation;

the elevation acquires the form of a club-head;

9 the second elevation begins to form;

10 — the second vesicle separates; the light spot becomes spherical; the crescent-shaped region disappears;

19 — completely separated yolk globules;

22— the beginning of secondary nearness of the yolk globules ; between them a light space ;

25— the greatest nearness of the yolk globules; the nuclei are not seen;

25a— no n- simultaneous division of nuclei into two primary yolk globules;

27— non-simultaneous division of yolk globules;

28-30 — gradual distortion of first fissure of division;

3 4 cross -shaped position of the globules of division;

36a — no n- simultaneous division of the nucleus into four yolk globules;

40— globules of division of the fourth stage (la- Id) are situated in the space between globules of the third stage CIA- ID) ;

43— extension of nuclei in the yolk globules of the third stage (1A-1D) ;

45— the yolk globules of the fifth stage (2a-2d) separated from the globules of the third stage (2A-2D) and situated between the latter;

46a — adjacent situation of nuclei, showing the origin of the yolk globules of the fifth stage from the globules of the third stage;

47 — the yolk globules of the sixth stage (la 2 -Id 2 ) separated from globules of the fourth stage (la 2 -Id 2 );

50 — the ninth stage of division.

Figure 40. War-nek* s drawings for his work on the development of gastropodan molluscs (development of a slug)

11 — in the place of the lost membrane of the nucleus, the oval light spot is seen;

12— the yolk has the form of a globule thickened from one side; the light spot is elongated;

13 — in the thickened side of the yolk the beginning of the formation of a fissure is seen; the light spot becomes more elongated;

14— the fissure twists the yolk diagonally; the light spot is extended;

15 — the fissure envelops half of the periphery of the yolk; at the ventral pole is the beginning of the formation of a fissure in the form of a deepening;

16 — deeper twisting of the yolk, viewed from the dorsal pole;

17 — the yolk globules are completely separated from each other; the light spot is hardly noticeable;

26 — the nuclei are deprived of membranes and begin to extend in a direction perpendicular to the longitudinal pole;

26a — still more distinct changes, the beginning of which is illustrated in Drawing 26;

29a— the stage of four yolk globules.

On the basis of experiments on ova which had been pressed in water, Warnek concluded that the structural changes in the nuclei depend upon the change of their chemical composition. The chemical changes that appear, in Warnek' s opinion, condition also the further transformations in the developing ova. After that when the fissure begins in the dorsal side (Figure 40, 14), it passes around half the periphery of the yolk; also in the ventral side, a deepening appears (Figure 40, 15) and the yolk is twisted by the meeting fissures. It acquires first the form of a biscuit, and then two united or even completely isolated globules (Figure 40, 17) . At the time of division of the yolk the light spot (nucleus) divides into two parts, each of which at first have caudiform processes, directed to the point of contact of the yolk globules (Figure 40, 16) . The processes quickly disappear, and the spot becomes spherical.

These phenomena, according to Warnek, characterize the first half of the second stage of division. At this time it is not possible to isolate the nuclei by (pressing) the yolk globules; from which it must be concluded that the nuclei are still deprived of membranes,

The second half of the second stage begins with the dividing globules moving nearer. Between them a noticeable cavity, formed from a transparent substance, emerges . Warnek considered this transparent substance the product of separation of the yolk globules. At the time the dividing globules are moving closer, the contours of the nuclei in them again become clear, i.e. the membrane appears (it is clearly noticeable in Li-max) by strongly refracting the color of the nucleolus. In Lymnaeus stagnalis the nuclei, at first, are situated near each other (Figure 39, 22), then separate, sink in the depth of the yolk globules, and at the end become invisible (Figure 39, 25) . Following the described phenomena each of the two yolk globules become pear-shaped. This outlines the passage to the third stage of division, during which the yolk is divided into four parts.

THE THIRD STAGE begins with changes in the nuclei, acquiring a biscuit or figure-eight shape (Figure 39, 25a); in the drawing it is seen that their division is not accomplished simultaneously: when one divides, the other keeps the form of a quadrant. The details of these changes can be traced only in the transparent ova of slugs. When the yolk takes the biscuit form, the nuclei are elongated (Figure 40, 26); following this the elongation and twisting of the yolk globules themselves takes place (Figure 40, 26a) . The twisting in Lymnaeus stagnalis and slugs begins in one globule earlier than in the other (Figure 39, 27), however, soon after this difference smoothes out. The boundary between the globules of division, corresponding to the first fissure, is at first straight (Figure 39, 27), and then becomes curved (Figure 39, 29, 30), and the yolk globules are situated crosswise in two planes.

The processes taking place in the nuclei were described by Warnek as follows: "The membranes of the nuclei disappear, the nuclei elongate, take an oval biscuit-shaped form, then bulge out, and finally each nucleus from the beginning of the division of the yolk globules is divided into three parts. From these parts of the nuclei only four are present in the globules of the division, and two gradually disappear in the fissures between the globules. The four nuclei at first have the form of a comet. When the division of the yolk globules is finished, the CAUDIFORM processes of the nuclei extend and the nuclei again acquire the rounded form" (pp. 146 - 147). The three parts into which, according to Warnek, each nucleus is divided correspond to the two daughter nuclei and to the achromatic figure of mitosis situated between them.

The final step of the third stage is the formation of the membranes around the nuclei and subsequent turning of the cross-shaped globules of division. Two of them are in contact with each other on the dorsal side, and the other two on the ventral (Figure 39, 34) . Between the yolk globules a rhomboid space appears during which this is especially clear in Limax.

THE FOURTH STAGE . At the beginning of the fourth stage the nuclei in the yolk globules of Lymnaeus stagnalis again become unnoticeable from outside. During the crushing out of ova it is possible, however, to see the changes occurring in the nuclei, which, as in the previous stage do not take place at the same time. In Figure 39, 36a it is seen that in the two globules of division which have the longitudinal form, one nucleus is biscuit-shaped, and the other consists of two isolated parts. After that, when the nuclei become elongated (in slugs this is seen also in the intact globules of division] , each yolk globule stretches and becomes pear-shaped. Then the twisting occurs in this form so that the newly forming globules are of unequal size, each separating a region of one third the size. The four smaller globules become displaced and are situated in the spaces between the larger two (Figure 39, 40) . "The remarkable reciprocal situation of the yolk globules," Warnek wrote, "is kept and is repeated in all the following stages; this allows one, without ever noticing the further formation of the yolk globules, to solve the question, what globules of division result from each present globule. During this it is necessary to keep in mind the position of the nuclei and the relative size of the yolk globules" (p. 153).

These accurate observations surpassed those investigations of nearly a quarter of a century afterwards. By the initiative of A. 0. Kovalevsky, the blastomeres of the dividing ova were given individual designations (in letters and numbers) , tracing during the process of development the fate of each blastomere and its derivatives. Warnek formally applied a less suitable and obvious method of designation of the globules of division and their descendants. He named the blastomeres arising in one or the other stage by the number of this stage, keeping for them the same designation also in the following stages of division. During this he mentioned that the yolk globules changed from stage to stage, so that, for example, during the transfer to the fifth stage the globules of the fourth stage were already unequal to the globules of the fourth stage at the moment of their formation. They decrease in size and are changed by chemical properties and internal structure.

THE FIFTH STAGE. In this stage the formation of the new globules of division follows the rules which also hold for the following stages of division. Instead of the sixteen yolk globules which must be present if each of the eight globules of the fourth stage is divided, here only twelve globules are found. This can be explained by the fact that during the fourth stage only four large globules are divided, and the other four small globules remain unchanged. Before the division itself the nucleus of the ventral (large) yolk globules become invisible, although on crushing out of the ova, it is seen that they elongate, i.e. they are present in a condition of division, while the nuclei or the dorsal (small) globules are not divided and remain round (Figure 39, 43) . The dividing yolk globules are stretched and twisted in the diagonal direction (Figure 39, 45). The newly arising yolk globules (again smaller in size than those which gave them the origin) are generally situated by the general rule, in the spaces between the large vegetative globules. The twelve globules of division present in the fifth stage are situated in three rows. The ventral row consists of four globules of the third stage, in the dorsal side four yolk globules of the fourth stage are present, and between the ventral and dorsal globules four newly arising yolk globules of the fifth stage are situated. The globules of the upper and lower rows stand against each other, and in the spaces between the globules of these rows the globules of the middle row are present. Concerning the origin of globules of the fifth stage from the globules of the third stage it is judged by the neighboring situation of their nuclei (Figure 39, 46a). In the second half of the fifth stage, as in the previous one, the smoothing of the surface of all globules of division and their nuclei becomes more distinct. Between the yolk globules a vesicular light space appears.

THE SIXTH STAGE. At the beginning of this stage four yolk globules of the fourth stage become more convex and the globules of the sixth stage separate from them. The yolk globules of the fifth stage remain the spaces between the globules of the third stage (Figure 39, 47). The total number of globules of division in this stage is sixteen.

THE SEVENTH STAGE is characterized by the three divisions of the globules of the third stage, giving rise to the four yolk globules of the seventh stage. The total number of globules of division is twenty.

THE EIGHTH STAGE. In this stage the four globules of the eighth stage are separated from the yolk globules of the fourth stage. The total number of yolk globules grows to twenty- four.

SUBSEQUENT DIVISION. In each of the following stages four yolk globules are formed. As an example the ninth stage can be employed. In the given drawing (Figure 39, 50) the dividing ovum is pressed, so it is possible to see a great number of globules of division. In the middle the yolk globules of the fourth stage are situated. To these last the oldest and large globules of the fourth stage are adjoined, moving far aside from each other by pressure. To the left of the globules of the third stage the globules of the fifth stage are present, obliquely from which the youngest globules of the ninth stage are twisted; they are situated in the spaces between the globules of the fifth and seventh stages. The globules of the seventh stage originate also from the globules of the third stage and are situated to the right of the last globules. Finally between the yolk globules of the fifth, seventh and fourth stages the globules of the eighth stage are present, arising as a result of a second division of the globules of the fourth stage.

Further Warnek carried out an analogical analysis of the fifteenth stage and established the origin of all globules present at this moment of division.

It is instructive to compare the genealogy of blastomeres, established by Warnek, in gastropodan molluscs with recent data. This comparison shows the complete agreement of Warnek 's results with recent data, as seen from the table. In it the designations applied by Warnek and the presently applied literal numerical designations are given.

The same comparison is given in Figure 41, where the contours of drawings 40, 45, 47 and 50 of Warnek are repeated and the data of the recent designations of blastomeres and their designations by Warnek are compared.

There is no doubt that Warnek completely and distinctly chose to follow the fate of the separated blastomeres ("yolk globules") and the participation of their descendants in the formation of organs of the developing animal. Selecting an irreproachable method by which this problem can be solved, Warnek in the first published investigations on the embryology of gastropodan molluscs described the first period of development up to the formation of the spherical multicellular stage, i.e. the blastula. Only at the end did he briefly mention the following period, when "some yolk globules share in the formation of first internal organ — the yolk sac." This first internal organ, the yolk sac, is of course nothing other than the endoderm of the embryo.

Concerning some details of division, Warnek noted that during the division of the nuclei of the yolk globules the nucleolus appears earlier than the nucleus when divided into two parts, therefore it is possible to find nuclei with two nucleoli. Warnek never saw the process of division of the nucleolus itself. The division of the nucleus in his experience was always accomplished by one plan, which in the early stages of divisions was the same as in the subsequent development of the embryo. This division in all conditions takes place after the stage of stretching of the nucleus, which then acquires the shape of a biscuit and a figure eight and is finally transformed into two separate nuclei.

The globules of division Warnek identified as the elementary organs, i.e. cells, and considered that their multiplication, beginning at the time of division, continued throughout the period of development and even through the entire life of the animal.

All the activity of the developing embryo and the animal forming from it is, in Warnek' s opinion, the result of that primary influence which the ovum ["yolk mass") is subjected to by the semen. "This influence," Warnek wrote, "has a purely chemical nature; therefore the explanation for this is still obscure for us; the vital phenomena must be given by physicists and chemists" (p . 168). "The effective element in the organism," Warnek continued,

is the material; this same material influences also outside the organism. If we explain this activity by chemical and physical powers, then there is no reason to deny the activity of these powers in the organism as well. Although these powers still cannot be completely explained, we do not possess the right to discard them and resort to the help of this power, which exists only in the imagination. Can we explain the phenomenon of crystallization? Why does sodium chloride always crystallize in the form of a cube, and pure carbon in the form of an octahedron? Is not the formation of globules of division, from the point of view of form, a kind of crystallization of organic matter? The successes of organic chemistry belong to us, because the processes accomplished during nutrition, respiration, and excretion are more satisfactorily explained by means of physics and chemistry than by means of a special vital power. This power has retreated into the dark field of our knowledge about the functions of brain and nerves and still dominates in the sphere of embryology. However, new histological directions make the study of the vital power even more unsteady in this sphere, so we are not far from the time when chemistry will completely exclude it from there as well. The concept of vital power must remain as a reminder of our previous ignorance. Only quite recently the influence of semen on the yolk was called dynamical; this expression shows only that the phenomena of fertilization could not be explained, (p. 170)

In these words Warnek exhibited the materialistic world view with complete clarity. He decisively objected against the dull idea of the vital power for the explanation of phenomena of organic life. The only way in which this explanation could be achieved Warnek considered to be the physico-chemical investigations of vital phenomena. Regarding fertilization as a chemical process, Warnek thought that the subsequent transformations of the dividing ovum have as their source continuous chemical changes. Of course, Warnek' s materialism has a mechanical character, but it is not excessively simplified vulgar materialism.

Warnek 's embryological opinions are expressed in his theses, the most important being:

The yolk mass after fertilization undergoes chemical changes, therefore the fertilization itself must be regarded as a chemical process. It causes changes in the unfertilized ovum which are necessary for further development of the embryo

Table The Genealogy of Blastomeres

Comparison of Warnek's designations— stage numbers (in parentheses! in comparison with the recent literal-numerical. Cln the square brackets the designation of the resulting blastomeres of the previous stage are repeated.)

Key:

1 . Stage of division by Warnek

5. The sixth

2. The third

6 . The seventh

3. The fourth

7. The eighth.

4. The fifth

Figure 41. Comparison of Warnek's designations of blastcraeres (stage numbers) with the recent literal-numerical designations of blastomeres . These and the other designations are put in the contours of Warnek's drawings .

During the development of the embryo, further changes of chemical processes take place.

The gastropodan molluscs are characterized by complete division.

The globules of division may be considered true cells.

In each stage of a division process four yolk globules are formed, i.e. the division proceeds not in geometrical, but in arithmetical progression.

Beginning with the third stage, the globules of division have unlike sizes.

Warnek's work produced a new page in embryology, directing the investigations of the history of individual development towards the study of subsequent changes of the fertilized ovum and the forming from it of blastomeres, and towards a study of the fate of the separate blastomeres and their descendants during the subsequent formation of the embryo. In this sense Warnek's investigation foreshadowed the works of A. 0. Kovalevsky and his countless followers who were studying either descriptively or experimentally the transformation of the elementary organs of the dividing ovum the blastomeres into systems of organs of the forming organism

N. A. Warnek was for a long time undeservedly forgotten. His classical work is rarely cited and not always mentioned even in the embryological summaries and textbooks, although he unquestionably deserved a place of honor in the history of Russian and world embryology.

The investigations of Grube, Nordmann and Warnek were monographical descriptions of the embryological development of certain representatives of the invertebrates. These works, with all their significance, did not answer, however, the requirements of comparison of the phenomena of development in different types of animals. The first attempt to include a wide number of invertebrates in embryological investigations was done by A. Krohn, whose services in this sphere are much undervalued. Krohn was so thoroughly forgotten that his name was not mentioned either in the encyclopaedias or in the biographical reference books. 30 The following circumstance is sufficient to attract the attention of historians of Russian science to Krohn.

30. For help given in researching biographical and bibliographical data about Krohn, the author thanks the biological section of Saltykov-Sedrin Gos. Publichnaya library in Leningrad, especially librarian V. L. Levin

During the first committee discussion of Baer's prize of the Russian Academy of Science in 1867, considering possible candidates for the prize, the following was stated: "If the matter concerned the crowning of previous scientific works, then the committee does not doubt that the prize belongs to one of our compatriots, Krohn, who was born in Petersburg. For many years from the fertile shores of the southern seas he collected a rich material which he investigated for the development of different animal forms. His investigation resulted in many excellent works which deserve respect from the scientists of all countries. However, the competition was to take under consideration only the works of the last three years. "31

The absence of biographical information about Krohn is compensated for by some bibliographical data. It is established that Krohn published no less than eighty works, 32 including some small monographs. Many of his publications were accompanied by indications of the time and place of performance of the corresponding work. With these indications one can form opinions about the life of Krohn, who spent no less than thirty years in travel with the aim of scientific investigations, zoological and embryological .

31. "Extract from the report of the committee on the discussion of the prize of secret adviser K. M. Baer, read in public meeting of the Academy of Science on February 17, 1867 by Academician Ovsyannikov, " NATURALIST (1867), Vol. 4, No. 7-9, pp. 98 - 104; No. 10 - 12, pp. 146 - 148. The extract cited is on p. 99.

32. The list of publications by A. Krohn is presented in the following :

1. CATALOGUE OF SCIENTIFIC PAPERS, compiled by the Royal Society of London (Vol. Ill, 1869- Vol. VIII, 1879) ;

2. w. Engelmann, BIBLIOTHECA HISTORICO-NATURALIS, Suppl . Band: J. V. Carus und w. Engelmann, BIBLIOTHECA Z00L0GICA: VERZEICHNIS DER SCHRIFTEN UBER Z00L0GIE, WELC'HE IN DEN PERIODISCHEN WERKEN ENTHALTEN VOR JAHR 1846 - 1860 SELBSTANDIG ERSCHIENEN SIND, Ed. I - II (Leipzig, 1861), 2144 pp.

33. Information on the dates of Krohn' s birth and death are taken from the brief bibliographical catalogue published by the Library of Congress in Washington.

August David Krohn was born in Petersburg in 1803.33 Concerning his birth and student years of study of Krohn we could not discoyer any information. One of his early works was produced in Vienna (1836); of the next work there is a memorandum, Petersburg (1 83 7) , Later on Krohn was in Heidelberg (18:59], and from 1840 he worked nearly continuously on the shores of the Mediterranean Sea and the islands of the Atlantic Ocean. In 1840 and later he was in Naples; from the autumn of 1844 to the spring of 1845 in Messina; 1848 in Nice; 1850 in Naples. In the beginning of 1835 and the winters of 1853/54 and 1856/57 he again was in Messina; in the winter 1855/56 and the spring and summer of 1865 he worked in Funchal (in Madeira) and in Santa Cruz (Tenerif e) . In December 1860, in May 1861 and in 1867 Krohn was in Nice, and in the first half of the year 1869 he was in Naples. In the intervals between travelling he lived in Paris (winter of 1851/52, spring of 1857) and in Bonn (summer months of 1851, 1853, 1855, 1857 and 1859, winters of 1859/60, 1864/65 and 1856/66, and also the second half of the year 1869) .

Concerning the last twenty years of Krohn 1 s long life of eighty-eight years there is again no information.

During his travels Krohn maintained contact with his country, as seen by the report of the conference of the Academy of Science in Petersburg, which presents the following records:

"Mr. August Krohn is a doctor who is famous for his works on anatomy and physiology. He has sent the Academy a significant collection of invertebrate sea animals which was collected by him near Naples, which, in quantity and quality, deserve the thanks of the Academy" (Report from December 16, 1842) .

"Dr. Krohn sent again, as a gift to the Academy Museum, two new collections, about one hundred species of fish, crustaceans and others" (Report of September 13, 1844).

On the 7th of November 1855 Krohn was recommended as candidate for corresponding member of the Academy of Science in Petersburg, hit was not elected. The biographical data given during this presentation shows only that he was born in Petersburg, lived abroad, and wrote about thirty valuable works dedicated to molluscs (IPaludina, Phyllirhoe and oephalpoda) ,

worms (SipunculuSj Syllisj Aloiopa) , and tunicates {Doliolum) , 34

During his travels Krohn entered into friendly relations with many great zoologists of the time, such as Johannes Muller, M. Sars, and Delle-Kyaie, and also the young investigators A. Kolliker, 35 k. Gegenbaur, 36 an( j a. Schneider. Johannes Muller (1801 - 1851) was a great German zoologist, embryologist and physiologist. For a long time he was the editor of the widely distributed journal ARCHIV FUR ANATOMIE, PHYSIOLOGIE UND WISSENSCHAFTLICHE MEDIZIN, in which Krohn published about thirty articles. Part of this information Krohn sent to the editor of the journal in the form of letters, containing information about his last works, and Muller published them in his ARCHIV which he sometimes accompanied by remarks and additions, always with a friendly and positive tone. In those remarks of Mill Her' s, discussions can frequently be found revealing his high regard of Krohn' s scientific activity.

Krohn willingly related his observations to the zoologists who were working at the same time with him along the sea coast C133) . His objective was to verify his data and to confirm their authenticity, and equally to help also the beginning investigators. His description of the planula hydromedusa Cladonema, Krohn accompanied with the remark that he showed them to Sars and Gegenbaur, thus certifying the accuracy of his observations.

34. Archives AN SSSR, fund 2, inventory 17, No. 6. The author is deeply grateful to B. E. Raikov. On a commission from him, extracts of reports of conferences of the Academy

of Science were carried out here and an Archives Certificate received.

35. "For accurate information about the structure of marginal bodies in medusa," Krohn wrote, "I am grateful to my young friend Kolliker from Zurich" (A. Krohn, "Einige Bemerkungen und Beobachtungen uber die Geschlechtsverhaltnisse bei den Sertularinen," ARCH. ANAT . , PHYSIOL. (1843), pp. 174 181} . Albert Kolliker was a well-known histologist and embryologist .

36. Karl Gegenbaur (1826 - 1903) later became a famous comparative anatomist and embryologist.

Anton Schneider (1831 - 1890) was a famous German zoologist, who in a work on the development of the mollusc Phyllirhoe bucephalumS? warmly mentioned "the repeated friendly directions" which he received from Krohn not only during the observations taken for that work, hit also throughout the time of their presence together in Messina in the spring of 1858. Significantly later, in 1867, Krohn met with Schneider in Nice; Schneider was interested there in larvae of any polychaetes which were covered with peculiar porous membrane. Schneider found that these larvae were well known to Krohn. In addition, as Schneider wrote, "Krohn, with his characteristic generosity, gave me the relevant pages of his journal that I might use the information contained in it at my discretion, expressing the hope that I could trace the further development of these larvae" (p. 498, footnote) .

Other works reveal that Krohn did not intend to publish his materials on the development of this polychaete, and agreed that Schneider would do this himself. Schneider wrote the work, its first part (description of the early stages) containing his own materials, and the second the results of Krohn 's observations on subsequent development. The work was published under the names of both authors, Krohn 's name in first place. 38

Helping to increase his material, Krohn showed at the same time extreme punctiliousness in relation to the strange data. This is illustrated by Krohn' s following remark on one of the early works about the structure of the nervous system in the echinoderms,39 as he sought to eliminating all shades of suspicion of incorrectness in relation to the published data of other investigators:

37. A. Schneider, "Uber die Entwickelung der PHYLLIRHOE BUCEPHALUM," ARCH. ANAT . , PHYSIOL. (1859), pp. 35 - 37.

38. A. Krohn und A. Schneider, "Uber Annelidlarven mit porosen Hullen," ARCH. ANAT., PHYSIOL. (1867), pp. 498 - 508.

39. A. Krohn, "Uber die Anordnung des Nervensystems der Echiniden und Holothurien im Allgemeinen," ARCH. ANAT . , PHYSIOL. (1841), pp. 1 - 13.

After I finished my observations on the nervous system of echinoderras and reported all the existed to Mr. Delle-Kyaie, I learned from this scientist that Mr. Van Beneden, a year before, had already discovered traces of the nervous system in echinus, information about which had appeared in L'INSTITUT. Because I could never get the proper issue of this journal, I should not be birred for not mentioning Van Beneden' s observations . (p. 7)

In all his works Krohn, with exceptional honesty and modesty, mentioned the results of the work of his predecessors, not fearing to recognize the superiority of foreign observations over his own. 40

No information was kept on personal events in Krohn 's life. He was not connected in his work either with scientific institutions or with universities. His life as a travellernaturalist hardly assisted the acquisition of a family of his own. To his relatives Krohn superficially referred in a letter to Johannes Muller:41 "After eight months absence, during which I spent April and May in Santa Cruz in Tenerife, I returned to Europe. The immediate cause for this was a forthcoming meeting with close relatives, whom I had not seen for some years" (p. 515).

In the first period of scientific activity (up to 1846) Krohn' s scientific interests were concentrated in the anatomy of vertebrates (fish, amphibia, birds) and invertebrates (coelenterates, annelids, arachnids, chaetognatha, molluscs, bryozoa, crustaceans, echinoderms, tunicates) . Incidentally to his morphological investigation, Krohn found parasites in the venous sinuses of cuttlefish (apparently diciemid) and described new species of pteropod and cephalopod molluscs.

Zootomical and zoological investigations were continued by Krohn, investigating the structure of protozoa, siphonophora,

40. Concerning the budding of the complex ascidian, Krohn wrote: "Mechnikov, with greater success than I, has traced the gradual development of buds" (Krohn, "Uber die Fortpflanzungsverhaltnisse bei den Botrylliden, " ARCH. NATURGESCH., 35 (1869), pp. 190 - 196).

41. ARCH. ANAT., PHYSIOL. (1856), pp. 515 - 522.

annelids, sea spiders, and arachnids, and describing new species of annelids, chaetopods, and gastropodan molluscs.

There is much authoritative evidence on the accuracy of Krohn's observations and morphological descriptions. These are sufficient to justify the opinion of Kovalevsky, 42 who was shared in the discussion of the nature of the so-called "ventral saddle" of sagitta. Krohn in 184443 considered this formation to be due to the nervous ganglion. Later, W. Busch44 corrected Krohn's opinion, and, in spite of the latter 1 s objection, Busch shared this point of view with Keferstein, R. Leuckart, Pagenstecher, and K. Gegenbaur. Keferstein did not agree with Krohn, but he gave credit to his anatomical investigations: "Krohn, as it is known, related this saddle's very great size to the nervous ganglion. I, together with Busch, do not doubt in that this excellent investigator was in the present question mistaken. "45

Kovalevsky, again investigating the anatomical structure of sagitta, strongly supported Krohn against the above mentioned authoritative zoologists. "I am against the new investigators," Kovalevsky wrote, "in considering Krohn correct concerning the ventral ganglion, and I hope to convince my readers of this also" (p. 135). "The ventral ganglion," he continued, "has the form of a long oval or quadrangular body with four large nervous trunks, from which two on the anterior end continue to the brain or the cephalic ganglion, connecting, as Krohn showed correctly, with the lateral nerves of the cephalic ganglion" (p. 136) .

42. A. O. Kovalevsky, "Embryologicheskie issledovaniya chervei i chlenistonogikh" (Embryological investigations of worms and arthropods) (1871), IZBRANNYE RABOTY (Izd. AN SSSR, 1951) , pp. 123 - 266.

43. A. Krohn, ANATOMISCH-PHYSIOLOGISCHE BEOBACHTUNGEN OBER DIE SAGITTA B I PUNCTATA (Hamburg, 1844), 16 pp. This work was published a year later in French (ANN. SC . NAT., 3 Ser., Zool., 3 (1845), pp. 102 - 116) and in English (ANN. NAT. HIST. 16 (1845), pp. 289 - 304).

44. w. Busch, BEOBACHTUNGEN UBER AN ATOM IE UND ENTWICKELUNG EINIGER WIRBELLOSEN SEETHIERE (Berlin, 1851), viii + 143 pp.

45. Cited in the article by A. O. Kovalevsky.

From 1846, Krohn frequently turned to the study of the phenomena of reproduction and development of different invertebrates - coelenterates, worms, molluscs, crustaceans, and mainly the echinoderms and tunicates.

The development of coelenterates is described in the following words — first, concerning the hydromedusa Cladonema and its\ development from the polyp Stauridium^ : the polyp forms buds from which the medusae are formed. Similar to oceanids in these medusae, as in Ooeanidae , in the walls of the stomach the sexual products develop. If mature males and females are situated in separate vessels, then after a short time on the bottom and walls of the latter ova can be seen, covered by a closely adjacent yolk membrane. That these ova are fertilized, Krohn judged by the absence of any embryonic vesicle and embryonic spot (nucleus and nucleolus) . Krohn mentioned I later the process of ovum division, though not describing it in detail, and referring to the fact that this process was observed already by Dujardin, who did not, however, evaluate/ its significance. Within two days after fertilization the formed larva is seen in the egg, which later on leaves the ovum membrane and swims with the help of cilia. The larva was characterized by a light superficial layer and included a dark, probably hollow nucleus (Figure 42, A). By its structure the larvae of Cladonema are similar with the young of higher organisms such as planulae (Aurelia, Cyanea, Cephea) . After two to five days the planula Cladonema becomes rounded, situated on the bottom, loses its cilia, and is transformed into a disk, not changing its internal structure. In the middle of the disk appears a round, hollow hillock, which grows later into a cylindrical process, composed of two layers present in planulae. On the upper end of the cylinder (rudiment of the polyp) four hillocks form, corresponding to the external ends of the future antennae. Already at this stage the first stinging capsules are seen (Figure 42, B) . Thus, Krohn concluded that "Stauridium resulted from the budding of the medusa Cladonema, which reproduced by ova; the young developing from the ovum is again transformed into the form of a polyp. The subsequent change of heteromorphic generation, from which more highly organized medusa develop must be regarded as a generic form and is considered, consequently, factually proved" (pp. 425 - 426).

46. A. Krohn, "Uber die Brut des Cladonema radium und deren Entwickelung zum Stauridium," ARCH. ANAT., PHYSIOL. 1853, pp. 420 - 426.

A preliminary report on these observations Krohn included in a letter addressed to Miiller.47

Figure 42. Planula hydromedusa Cladonema (A) and the polyp developed from it Stauridium (B) by Krohn .

Two years later Krohn published a report about the structure of the early stages of development of the medusa Pelagic. noctitucaA^ At first he found near Messina invertebrate medusae similar to ephyra scyphomedusa, separating from "polypform helminths" (scyphistoma) , and he found also earlier larvae.

47. A. Krohn, "Uber einige niedere. Thiere. Brief liche Mitteilung a. d. Herausgeber, " ARCH . ANAT . , PHYSIOL C1853) , pp. 137 - 141.

48. A. Krohn, "Uber die friihesten Entwickelungsstufen der Pelagia nootiluca," pp. 491 - 497. ARCH. ANAT., PHYSIOL. (1855),

The supposition that they were stages of development of Pelagia noctiluca was completely confirmed. After many unsuccessful attempts, Krohn could carry out artificial insemination. As a result of division ,larvae formed having a cylindrical, usually stretched form (Tigure 43, A). The end of the larvae (a) which is directed forward while swimming is rounded, and the other (b) is chipped off. The surface of the larva is covered by short cilia. In the blunt end occurs a depression with an extremely small, round orifice is seen. This orifice is the mouth, which leads to the round, clearly outlined cavity of the stomach (c) , occupying the posterior third of the body. Tne mouth and stomach, in Krohn 's words, are already clearly differentiated already in the natural forms, but it is still a non-hatched embryo. However in the present stage the stomach is shorter and more rounded than in the free larvae.

Mechnikov rated highly this discovery by Krohn. In his monograph EMBRYOLOGICAL INVESTIGATIONS ON MEDUSA (1866), 49 he noticed the weak interest in embryology by the zoologists of the mid-nineteenth century. He wrote:

Even important generalizations, such as the similarity between the two layers of coelenterates and the embryonic layers of the higher animals, emphasized by Huxley, and significant facts, such as Krohn' s discovery of the formation of a stomach in pelagia by a stretching of the blastomeres, remained without attention and in a lower plane, (p. 284)

The correctness of these observations by Krohn was later confirmed by Kovalevsky and Mechnikov. In this work also, Krohn reported one important discovery: "On the contrary to Medusa aurita and other above-named medusae, "50 he wrote, "Pelagia noctiluoa develops without the generation of helminths" (p. 469). Krohn could trace how the swimming planula Velagia, while not settling on the bottom and not transformed into scyphistomae, forms on the edges of the mouth orifice processes, later becoming part of Ephyra (Figure 43, B and C) with marginal sensory bodies. The citation of this discovery can be found either in later investigators of the embryology of medusae (for example, KovalevskySl and Mechnikov (134)], or in textbooks. 52

49. Cited in I. I. Mechnikov, IZBRANNYE BIOLOGICHESKIE PROIZVEDENIYA (1950), pp. 271 - 472.

50. Krohn compared the development of Pelagia with the development of Medusa, Cyanea, Chrysaora, Cephea, and Cassiopea .

In 1861, during his residence in Nice, Krohn observed the reproduction and development of hydromedusa Eleutheria , 53 The ova arise between ecto- and endoderm and there they develop into the larval stage of larva. Ectoderm, covering the embryonic chambers, swells into hillocks, which subsequently break and release young. The larvae are considered typical planulae and are subjected to the same transformation as in the planula Cladonema.

The budding occurs not only in asexual, but also in completely differentiated bisexually related individuals. Krohn described the process of budding, and noticed that the budding begins in very young individuals, which are still not completely separated from the maternal individual.

51. A. O. Kovalevsky, "Observations on the development

of Coelenterata," IZV. OBSHCH . LYUBIT. ESTESTV. ANTROP. I ETNOGRAFII, 10 (1874), vyp. 2, pp. 1 pp. 1 - 36. To the work of Krohn there is reference on p. 7. ^

52. K. N. Davydov, TRAITE D 'EMBRYOLOGIE COMPARES DES INVERTEBRES (1928), p. 78. The drawings given by Davydov (Figure 36) illustrating the development of Velagia were taken by him from the work of Delap, published more than fifty years after Krohn' s. They are not a bit better than Krohn ' s drawings .

53. A. Krohn, "Beobachtungen iiber den Bau und die Fortpf lanzung der Eleutheria Quatref. , " ARCH . NATURG., 27 (1861), 1, pp. 157 - 170.

Figure 43. Later stages of development of medusa Pelagia noot-iluca (by Krohn) .

a — anterior; b— -posterior end of the body; stomach.

The development of worms54 Krohn described in many separate reports. In 1851 he wrote an article on the reproduction and larval stages of "gefirei," 55 He established the fact of dioecious Phasoolosoma and described the structure of mature ova of Sipunculus nudus . Attempts at artificial insemination of these ova were unsuccessful, and Krohn had to be satisfied with the study of the larvae of Sipunculus caught in plankton, whose description constituted the final part of the work. Two small remarks by Krohn are concerned with the vegetative reproduction of the annulated worm Syllis and Autolytus . 56 He found in them this change of sexual and asexual reproduction, which permitted comparison with true alternation of generations. Many years later 57 Krohn again turned to the study of reproduction in sillids, describing the new viviparous species of polychaeta of this genus.

54 . Of the types of worms known in the mid- nineteenth century, many were distinguished later on in independent groups of forms, including phoronids and chaetognaths , and are so listed.

Other of Krohn 's reports separate information about the development of nemertineans, phronids, and chaetognaths . The description of larvae and partial transformation of the first two forms constitute the contents of a special article^ (135) . On the question of the development of nemertineans inside pilidium, Krohn inclined to the opinion that pilidium is considered a helminth, giving origin to worm-shaped sexual generation. Actinotrocha, in Krohn' s opinion, is a larval stage of any worm, tentatively relating to echiuroids. The process itself of the transformation of actinotrocha he did not observe and noted only the disappearance of the larval organs and the concentration of antennae in the circumoral corona.

In his excellent investigations on the structure of chaetognaths, Krohn added the study of their development.

55. A. Krohn, "Uber die Larve des Sipunoulus nudus nebst vorausgeschikten Bemerkungen liber die Sexualverhaltnisse der Sipunculiden," ARCH. ANAT . , PHYSIOL. (1851), pp. 368 - 379.

56. A. Krohn, "liber die Erscheinungen bei der Fortpflanzung von Syllis prolifera und Autolytus proKfer," ARCH. NATURG., 18, 1 (1852), pp. 66 - 76; "Uber die Sprossling von Autolytus prolifer Gr.," ARCH. ANAT., PHYSIOL.

(1855) , pp. 489 - 490.

57. A. Krohn, "Uber eine lebendiggebarende Syllisart," ARCH. NATURG., 35 (1869), pp. 197 - 200.

58. A. Krohn, "Uber Pilidium und Actinotrocha," ARCH. ANAT., PHYSIOL. (1858), pp. 289 - 301.

In a letter to Johannes Miiller sent on February 2, 1853 from Messina, 59 he reported: "I have at the same time studied the development of sagitta. What Darwin has said about it relates to the development of any fish" (p. 141) (136). Krohn did not publish any further special work on the development of sagitta.

Of Krohn' s two articles on Cirripedia, one concerns the structure of the cement gland of Lepas anatifera and Conohoderma virgata and the anatomy of the female genital system of Lepas and Balanus trintennabulwn . The other^O includes some data about larval development. Krohn described the intermediate stage between the young larva which is similar to the nauplius of the copepods and the late cirripesshaped larva. The work is illustrated with graphs of very young larva of cirripeds, and also larvae of Balanus species and Lepas antifera.

The development of gastropodan molluscs (pteropods and heteropods) was the subject of four reports, the last with the character of a detailed monograph. ^1 in these investigations his main attention is given to a detailed description of larvae of pteropods (subclass opisthobranchia) : Cymbulia Peronii, Tiedemannia neapolitana, Gastropteron Meokelii 3 and also the larvae of carinate molluscs (subclass prosobranchia) Pterotraohea (two species) , Carinaria mediterranean and Fir-iolides (Figure 44) .

59. ARCH. ANAT., PHYSIOL. (1853), p. 137.

60. A. Krohn, "Beobachtungen iiber die Entwickelung der Cirripedien," ARCH. NATURG . , 26, 1 (1860), pp. 1 - 8.

61. A. Krohn, "Beobachtungen aus der Entwickelungsgeschichte der Pteropoden, Heteropoden, und Echinodermen. Brief 1. Mitt. a. d. Herausgeb.," ARCH. ANAT., PHYSIOL. (1856), pp. 515 - 522; "Beitrage zur Entwickelungsgeschichte der Pteropoden und Heteropoden," ibid . (1857), pp. 459 - 468; "Uber die Schale und die Larven des Gastropteron MeckelM," ARCH. NATURG., 26, 1 (1860), pp. 64 - 68; BEITRAGE ZUR ENTWICKELUNGSGESCHICHTE DER PTEROPODEN UND HETEROPODEN (Lepizig, 1860),

46 pp.

Figure 44. A-Larva Ctio from the dorsal side with not completely straightened fans of sailing; B^— extracted from ovum larva F-ivioZides , view from above (by Krohn) .

The accuracy of Krohn's observations concerning the structure of the larvae of gastropodan molluscs is noted in recent books on comparative embryology, For example, K. N. Davydov wrote that "Already, long ago, zoologists turned their attention to the development of gastropodan molluscs, and Krohn and Nordmann left for us memoirs which even at present do not lose their significance" (p. 625) .62 ^ n( j elsewhere: "It is known that the classical case of heteropods (_Firzolid.es) was described by Krohn in 1860" (p. 651).

A significant place in Krohn's scientific heritage is occupied by his investigations on the development of echinoderms; they were described in no less than ten special reports and transitional notes in works describing other subjects. His systematic study of the embryology of echinoderms Krohn began in 1848 at the time of his three-month stay in Nice. In February-April he experimented with the artificial insemination of the ova of the echinoid Echinus lividus . His observations were compared with data published shortly before by Derbes, 63 w ho also studied the development of ichinus brevispinosus .

The mature ovum of Echinus lividus, according to Krohn, is covered by membrane (chorion) and composed of yolk (this term Krohn called the ooplasm with nutritional inclusions), with an embryonic vesicle (nucleus) and embryonic spot (nucleolus) . Derbes assertion that the embryonic vesicle disappears in the mature ova up to fertilization, Krohn considered the result of Derbes' insufficiently thorough investigation. Within approximately half an hour after fertilization of the ova, the, membrane is separated from the yolk, a phenomenon, which Krohn explained by processes of endosmosis and exosmosis: "the ovum membrane absorbs the fluid from the surroundings and again gives it, to its internal surface" (p. 6). After fertilization the embryonic vesicle and the embryonic spot are no longer seen. In the place of the ovum nucleus, not far from the surface of the ovum, Krohn saw an empty vesicle. With Baer and Derbes, he considered this vesicle the nucleus of the fertilized ovum and suggested that the process of yolk division can begin only after the appearance of this nucleus. Within three to four hours after fertilization the division of the nucleus begins. Referring to Baer's excellent observations, Krohn left out the description of the initial processes of the division. In the conclusion of the monograph he noted that the result of the yolk division is the formation of cells, from which the body of the embryo is formed, because the globules of division are unnoticeably transformed into cells of the developing larva. The evidence of this transformation is found in the contents of the cells; "numerous molecules inside the last substance are nothing but yolk granules, from which the division globules are previously formed" (p. 29). "In the same genetic relation, the nuclei of the cells are related to the vesicular nuclei of the division globules" (p. 30).

62. Davydov, TPAITE D ' EMBRYOLOGIE .

63. Derbes, "Observations sur le mecanisme et les phenomenes qui accompagnent la formation de l'embryon chez l'Oursin comestible," ANN. SC . NAT., 3 Ser.,

8 (1847) , pp. 80 - 98.

64. a. Krohn, BEITRAG ZUR ENTWICKELUNGSGESCHICHTE DER SEEIGELLARVEN (Heidelberg, 1849), 36 pp.

Krohn prefaced the characteristic of the fully formed echinus larva with the development of the larva, suggesting that knowledge about the final development must help the understanding of the phenomena leading to it. The external form of the pluteus, the structure of its skeleton and the digestive system are represented in the drawings and are described as follows. The formed larva, within eleven days after the fertilization, is pear-shaped (Figure 45, F) ; it possesses two pairs of limbs: the short ee and the long dd. On the convex side, facing the mouth £, and situated between the limbs, the anal opening c^ is present, although frequently closed, which is why Johannes Miiller missed it in the larvae of ophiuroids and echinus. The bilateral symmetry of the larva is absolutely clear and is expressed in the pairing of limbs and the calciferous skeleton carrying their branches, in the situation of the mouth and the anus in the plane of symmetry. Inside the larva is a cavity extending to the end of the limbs; the digestive tract lies in this cavity, surrounded by loose fibrous tissue. The larval surface is covered with skin; the last is formed from twinkling cells, in each of which there is a nucleus with nucleolus. The calciferous skeleton consists of four pairs of toothed branches (Figure 45, G) , the longest branches gg_ are club-shaped, the next pair is found in the long limbs hh, another pair in the short limbs kk, and the last pair H_ is situated across the longitudinal axis of the larva.

The digestive canal consists of three parts, the anterior (the pharynx) , the middle (stomach) and the posterior (intestines), all covered by cells with cilia, similar to the cells of the skin. The digestive canal is attached to the body cavity by fibrous tissue; it forms a network united with the internal surface of the skin. In the junctions of the network, nucleus-like formations are situated; they are numerous also under the skin, in the neighborhood of the calciferous skeleton. Krohn noted Johannes Miiller's error when he assumed them to be strong fibers instead of nerves, and the nuclei of fibrous tissue instead of nerve ganglia. The larva swims with its limbs, mouth opening forward; its movement is carried out by the activity of the cutaneous twinkling cilia, which also drive into the mouth food particles suspended in the water.

The formation of the larva described here takes place as follows. After the division is completed, the young spherical larva rotates in the ovum membranes with the help of the long cilia which cover all the surface of its body. In the larva at this time can be observed a closed central cavity and cover, which can be differentiated, forming the wall of the latter. Krohn erroneously considered that the wall of the body consists of many layers of cells. Within a day after fertilization, when the number of the cover cells becomes sufficiently large, the ovum membrane is torn and the larva begin to swim. Soon after hatching it acquires its ovoid form (Figure 45, A); during swimming its narrow end is directed forward.

In the body cavity of the larva, from the side of the blunt end, an accumulation of closely situated dark bodies, similar to the nuclei, is seen. The number of these nuclei at first is small, but it quickly increases so that they are found filling half of the body cavity of the larva, toward its blunt end (Figure 45, A,e) . Later, nuclei are separated from each other and distributed evenly in the body cavity, and then partially accumulate not far from the rudiments of the calciferous skeleton. After this, the nuclei become angular or fusiform and begin their transformation into the fiber of the reticular tissue which strings the body cavity and holds the digestive tract.

Figure 45. Development of echinus, Echinus liwidus (by Krohn) .

A — larva shortly after hatching: a — blunt pole; b — sharp pole; c, c — cover; d — central cavity; e — accumulation of "nucleuslike formations" from which the fibrous tissue is later formed.

B — "ideal sketch" of the larva, already having the form of the body with three surfaces: a, b, c — anterior, posterior, and upper surfaces; d — anterior angle; e, e — posterior angles; f — lower angle ; g — anus .

C— — cross-section of this same stage of development, in which for elucidation of the passage the previous apple-shaped form was drawn: a, b, c, d, e, f, g — as in figure B; h — rudiment of the digestive tract in immature form; k — its rudiment in later form.

D — larva of the following form, back view: a, b — posterior and upper surfaces; c — anus (back passage) ; gg, 11, kk — rudiments of club-shaped, arch-shaped, and transverse branches of calcareous skeleton.

E — later larva: a, b : c, g, k, 1 — as in figure D; dd — rudiment of posterior limbs; hh — first traces of hydrants in it.

F — larva of pear-shaped form, back view: dd — posterior limbs; ee — anterior limbs; f— -mouth; q — -anus; ssss — cilia apparatus.

G — calcareous skeleton of the formed larva, represented in

an isolated view: gg — club-shaped hydrants; hh — hydrants of anterior limbs; kk — arch-shaped hydrants; 11 — transverse hydrants .

From Krohn's description it is clear that he saw, for the first time, in the cavity of echinus division that accumulation of cells, which was called by the latest embryologists the primary mesenchyma. He correctly determined the fate of these cells in larval development. This discovery of Krohn's was so thoroughly forgotten that Mechnikov, who was well acquainted with the old embryological literature, attributed it to Selenka, whose work was published exactly thirty years later after Krohn's monograph. 65

"The development of Echinus micro tub eraulatus ," Mechnicov wrote, "was studied by Selenka. The first differentiation of the embryonic layers begins with the bulging of the lower cells of the blastoderm. Until the beginning of their protrusion they form a number of wandering cells, which later develop into the cutis and are considered mesodermal or mesenchymal cells. "66

Krohn observed that after nearly thirty hours after fertilization the following important changes take place in the larva of Echinus lividus . In the center of the blunt pole a small hole-like deepening appears. The blunt pole widens and thickens; the hole in its center becomes deeper and wider, so that the body of the larva becomes similar in form of an apple. The more enlarged hole "formed as a result of that," Krohn wrote , caused the skin in this area gradually to protrude (EINSACKT ODER EINWARTSSTULPT) into the cavity of the body. The protrusion (EINSACKUNG) submerged deeper in the body cavity and extended into a canal which finally reached the walls of the body cavity toward the blunt pole. The sac which appeared by this means stretched through the body cavity (Figure 45, C, h, k3 and is the rudiment of the digestive cavity. The edge or circumference of the primary hole becomes a leading opening in the canal, which is the anus. In this view's favor — on the manner of appearance of the digestive tract — is the fact that it also indicates that the wall of the canal is absolutely equivalent to the skin in thickness and structure. (p. 18)

65. E. Selenka, "Keimblatter und Organanlage bei Echinicen," ZTS. WISS. ZOOL.,, 33 (1879) .

66. I. I. Mechnikov, "Vergleichend-embryologische Studien.

3: Uber die Gastrula einiger Metazoen," ZTS. WISS. ZOOL., 37 (1882) , pp. 286 - 313.

Krohn's discovery of the nature of the formation of the larval intestine of echinus undoubtedly possesses outstanding significance. This, unquestionably, is the first description of the invaginated gastrulation phenomenon. Its study subsequently played a great role in the progress of comparative embryology. Comparative analysis of methods of separation of the endoderm is included in the basis of Kovalevsky f s evolutionary concept about the formation of the embryonic layers, and also in the basis of Haeckel's gastrula theory. Krohn's priority in this question was not definitively underlined. Mechnikov, in the article just cited, wrote the following.

Derbes (1847) described the formation of the larva of Echinus esoulentus and mentioned a stage in the form of a double sac with skin layer in which the caecum opened to the outside. Twenty-five years later, Haeckel gave this the name gastrula, which was accepted by scientists all over the world. Derbes thought that the opening of the rudiment of the intestine was the mouth, but August Krohn (1849) showed that it corresponded to the anus of the pluteus. He described the process of protrusion itself.

Krohn referred to Derbes' observations: "The reader can form an excellent concept of the gradual formation of the digestive tract just described by looking at Figures 13 and 14 in Derbes' article; however, the author apparently did not pay attention to the process of formation itself" (p. 19). The following is written by Derbes: "The spherical form of the larva is changed by pressure at one point of the surface. Gradually this pressure becomes more pronounced, and its center is penetrated by an opening which leads to a rudiment of the intestinal cavity. Beginning from this moment, the movement of this opening is always directed forward and, later, upwards. . . that is, the mouth looks towards the zenith" (pp. 91 - 92). It is clear that Derbes did not put the deepening on the surface of the spherical larva in genetic relation with the formed intestine. According to his opinion, the opening formed in the center of the deepening united in an unknown way the developed rudiment of the digestive tract with the external world. Krohn pointed also to DerbSs' mistaken assumption that this opening was the mouth. He established that the opening in the area of protrusion is the anal opening, and the mouth is formed in another place significantly later (on the fourth day after fertilization] .

Further observations of Krohn are concerned with the changes in the larval form" as it becomes bilaterally symmetrical (Figure 45, B and C) . He described the formation of limbs and the calciferous skeleton (Tigure 45, D and E) , which gradually acquires a different configuration.

In the following year, Krohn repeatedly returned to the study of development of the different echinoderms and published many reports on this subject, One of these reports considered the development of the holothurian and echinus. 67 The larvae of holothurians (Holothuria tubulosa} were obtained from plankton, because attempts at artificial insemination proved unsuccessful. The youngest larva observed by Krohn "is similar to an elongated egg (Figure 46, A); in its sharp pole there is an opening leading to a sac-like protrusion in the body and an ampul la- shaped canal widening at the end Ik This sac is the rudiment of the digestive tract, the opening doubtlessly is the anus" (p. 345). Krohn noticed that the larva of Holothuria tubulosa, at this stage, is very similar to the larva of Echinus lividus described earlier by him (1849) . Similar to the latter, the larva of Holothuria tubulosa is covered by cilia, and with their help it swims with the imperforate pole forward. The surface of the body and the digestive tract consist of cells which, with their nuclei, become noticeable with the addition of fresh water. In the body cavity, as in the larvae of Echinus lividus, fibrous tissue with fusiform cells is found. Later (Figure 46, B) on the abdominal side of the larva a depression appears — which is the future transverse fissure of ausicularia; in this fissure the mouth opening later appears. Later the body acquires a kidney-shaped configuration (Figure 46, C) . The digestive tract, at this time, forms the rudiments of the three parts, pharynx e, stomach d and intestines c. The appearance of the mouth opening coincides with the beginning formation of the ciliary strings in the auricularia. At this stage there is some data about the transformation of the Echinus lividus .

67. A. Krohn, "Beobachtungen aus der Entwickelungsgeschichte der Holothurien und Seeigel," ARCH. ANAT . , PHYSIOL. (1851) , pp. 344 - 352.

Krohn's other reports on the development of echinoderms briefly designate some representatives of the type68 or species. 69

Special attention must be given to Krohn's investigations on the development of tunicates. Originally his interest was attracted by Salpa, in which the wonderful phenomenon of the alternation of sexual and asexual generations had already been recognized. This discovery belongs to the poet Adalbert Chamisso (1781 - 1838) . With the Dorpat-born zoologist J. F. Eschscholtz, he traveled around the world on the Russian ship RURICK. Chamisso published the results of his investigations in "On Some Animals of the Linnean Class of Worms, noted during a world tour, performed by Count N. Romanzoff, under the command of Otto von Kotzebue, from 1815 to 1818, Part I: On Salpa. "70

68. A. Krohn, "Bemerkungen uber einige Echinodermenlarven, " ARCH. ANAT., PHYSIOL. (1851), pp. 353 - 357; "Uber die Entwickelung der Seesterne und Holothurien (Brief 1. Mitt. a. d. Herausgeb . ) , " ibid . (1853), pp. 317 - 321; "Beobachtungen iiber Echinodermenlarven (Brief 1. Mitt, a. d. Herausgeb.)," ibid . (1854), pp. 208 - 213; "Uber neuen Entwickelungsmodus der Ophiuren," ibid . (1857), pp. 369 - 375.

69. A Krohn, "Uber die Entwickelung einer lebendiggebarenden Ophiure (Brief 1. Mitt. a. d. Herausgeb.)," ARCH. ANAT. PHYSIOL. (1851), pp. 338 - 343; "Uber die Larve von Spatangus purpureus (Brief 1. Mitt. a. d. Herausgeb.)," ibid . (1853) , pp. 255 - 259; "Uber die Larve des Echinus brevispinosus ," ibid . (1853), pp. 361 - 364.

70. DE ANIMALIBUS E CLASSE VERMIUM LINNEANA IN CIRCUMNAVIGATIONE TERRAE AUSPICANTE COMITE N. ROMANZOFF DUCE 0TT0NE DE KOTZEBUE ANNIS 1815, 1816, 1817, 1818 PERACTA OBSERVATIS ADELBERTUS DE CHAMISSO, Fasc. primus: DE SALPA (Berlin, 1819) , iv + 24 pp.

Figure 46. Three stages of the development of the sea cucumber Holothuria tubulosa (by Krohn) .

A and B: a — anus; b — digestive cavity, Id — anus; c, d, e — rudiments of the

estine, stomach and pharynx.

C: inte

The alternation of sexual and asexual generations in Salpa was described by Chamisso as follows:

The species of Salpa is found in double form: each generation of the species is dissimilar to its parents, but through birth posterity is similar to the last, so that any Salpa differs from its parent but is identical with its grandparents. Both forms are similar to headless molluscs, hermaphrodites or the female sex. Both of them are viviparous, but one of them is a solitary animal, the originator of many descendants . The other represents a complicated branch consisting of animals, each united with the others by the necessary connection which gives birth to one descendant. These changed forms of the unchanged species are called solitary (Proles solitaria) and aggregated or colonial (Proles gregata) generations, (p. 2)

After the discovery by M. Sars^l of the analogical change of generations in scyphomedusa, Steenstrup united these facts to produce one biological regularity. Steenstrup 's general conclusion was highly regarded by his contemporaries, in particular by Baer.72 Krohn also gave great significance to Chamisso's discovery and Steenstrup 's ideas. He made it his task to study in detail the reproduction and development of Salpa. To do this, he settled for many months on the coast of Sicily, where the sea provided him the necessary material. Krohn put the results of his observations into a special work, 73 in which, first of all, he completely confirmed Chamisso's observations, by distributing them over seven species of Salpa which were, for the first time, partly described by him. The comparison of the solitary and colonial forms (Proles solitaria and Proles gregata, in Chamisso's terminology) allowed Krohn to regulate the taxonomy of this group of tunicates. He showed that salpae described under different names frequently proved to be different stages of the development of one and the same species (137) . Later, Krohn gave the characteristics of the structure of the heteromorphic generation, and also described the ovum, the seminal glands, and the process of fertilization in the sexual generation.

Within the present book, the greatest significance is placed on the section in Krohn' s article (111) in which he discussed development of the embryo in the maternal organism. After fertilization, the embryonic vesicle and the embryonic spot disappear, after which the ovum enlarges in size and acquires a regular spherical form. This was according to Krohn, who was not completely convinced of its authenticity. Sometimes the ovum is not seen like that, and in its place a round body appears, raising a region of tunica of the mother and jutting into its cavity in the form of papilla. This body, Krohn wrote, is nothing other than the rudiment of the placenta which, by deepening in the cavity of the body of the maternal organism, enters in connection with two of its blood vessels. Only after the formation of the placenta does the embryo begin to develop, at first in the form of a very small body appearing on the summit of the placenta under its cover (138) . In this rudiment of the embryo all organs of the last are developed; "however," Krohn wrote, "all that concerned its development during the first period remained for me almost completely unknown" (p. 123). He could only establish that one of the first organs of the embryo by the time of appearance is "the respiratory cavity." The embryo changes from compact to hollow, following which the rudiments of the branchae and nervous ganglion are already seen, while the organs "visceral nucleus" and heart become noticeable only later. Only after that does the embryo acquire a definite form; the anterior and posterior openings appear in it. At the end the embryo becomes more voluminous than the placenta, and all its organs intensively enlarge, especially the nervous ganglion, from which numerous nervous branches grow. At the same time muscular strips and blood vessels appear, which are not completely formed.

71. M. Sars, "Uber die Entwickelung der Medusa aurita und Cyanea caprtlata," ARCH. NATURG . , 7 (1841), pp. 9 - 34.

72. See Chapter 23.

73. A. Krohn, "Observations sur la generation et le developperaent des Biphores (Salpa)," ANN. SC . NAT., 3S6r., Zool., 6 (1846), pp. 110 - 131.

Krohn' s concluding paragraph of the work is dedicated to the processes of budding in the asexual regeneration of Salpa, and to the formation of colonies; the character of the last varies in different species. Here the description of the stolon and the embryos is given, situated along it so that their axes cross the stolon at a right angle. These embryos develop in definite succession, depending on their situation on the stolon.

The development of salpa, especially the formation of their embryos from fertilized ova, represents one of the most difficult principles of embryology. Krohn' s investigations began this study and recent opinions are credited to many Russian embryologists at the end of the nineteenth and the beginning of the twentieth century, including A. 0. Kovalevsky, M. M. Davydov, A. A. Korotnev, and V. V. Zalensky. 74

Six years after the publication of the above-mentioned work, Krohn published an article presenting the results of his investigations of the little-studied group of tunicates, the doliolum.75 Q U oy and Gaimard made a voyage on the

74. "The first investigations of the development of Salpa go back to. Krohn," K. N. Davydov wrote in his handbook CTRAITE, p. 867) .

75. A. Krohn, "Uber die Gattung Doliolum und ihre Arten," ARCHIV. NATURG., 18 (1852), pp. 53 - 65.

ASTROLABE 7 ^ to Road Island, Ambon (in the Moluccas), and to the coast of the Vanikoro Islands (between the New Hebrides and the Solomon Islands) . During this time they discovered this small transparent tunicate, which they described and presented only incompletely, and for which they suggested the generic name Doliolwn.

Later T. Huxley, on a tour around the world aboard the ship RATTLESNAKE, saw doliola in the southern part of the Pacific Ocean and described their structure more exactly and in more detail than Quoy and Gaimard,77 but in his notes the male genital glands were given for individuals of sexual regeneration.

Krohn, for the first time, discovered the presence of doliola in the Mediterranean Sea (near Messina and Naples) , studied the structure and described three new species. According to Krohn, doliola "are free living ascidians, but in many respects are similar to salpa and form, therefore, an interesting intermediate link between both these orders of tunicates" (p. 53). From Krohn's description, the structure and reproduction of doliolum, according to the majority of the features, must be related to salpa; this applies also in the present taxonomy.

Krohn observed that from the ova of doliola cercarialike larvae develop which later undergo metamorphosis . The peculiarities of the larvae are connected, according to Krohn, with the mode of life of the tunicates more than to ascidians, which are in their adult condition fastened motionless to the substrate. In accordance with this, in the ascidian larvae the tail disappears early, but in the larvae of doliola it remains throughout metamorphosis and serves as an organ of movement. The process of reduction of the tail in the larvae of doliola takes place as in the larvae of ascidians . In the latter the disappearance of the tail was noticed for the first time by Milne-Edwards in an example of the colonial ascidian Amouruoium proliferum, and was described in more detail by Krohn for Phallus-La mammillata .

76. VOYAGE DE DECOUVERTE DE L' ASTROLABE EXECUTE PAR ORDRE DU ROI PENDANT LES ANNEES 1826 - 29 SOUS LE COMMANDEMENT DE M. J. DUMONT D'URVILLE. ZOOLOGIE PAR MM QUOY ET GAIMARD, vol. 3 (1834).

77. T. Huxley, "Remarks upon Appendicularia and Doliolum, Two Genera of Tunicates," PHIL. TRANS. ROY. SOC . LONDON (1851), pp. 599 - 602.

The metamorphosis of doliola was again studied by Krohn on the species Doliolum Nordmanni. Krohn represented two stages of transformation; Figure 47, A represents the stage when the tail of the larva has not begun reduction; and Figure 47, B, the larva with shortened tail. Until metamorphosis the tail of the larva is tapered, with the two ends covered with gelatinous membrane a_; its axis d_ is composed of cuboidal cells situated in one row, so that it seems to be segmented. The root of this axial shaft penetrates into "the vesicular appendix" c_, lying under the digestive tract of the larva. This vesicle decreased simultaneously with the reduction of the tail and at the end it disappears (139) . In the stage represented in Figure 47, B, all organs in the larva are already differentiated; on its dorsal side there is the placing of the stolon £.

Krohn ! s description of the structure of the larva of doliolum and its transformation distinctly shows that he saw in it all the principal features of organization, on the basis of which the doliolum was later counted as a type of chordate (subtype tunicate, class salpa) : the presence of the reduced cord at the time of metamorphosis ("axis of tail"), the situation of the nervous ganglion o_ on the dorsal side and the heart m on the ventral side.

Correct evaluation of Krohn ! s investigations was given by V. N. Ulianin in the classic monograph on doliola, first published in Russian, and two years later in German.' 7 ** Ulianin wrote the following: "Soon after the appearance of Huxley's article the doliolum was found in the Mediterranean by Krohn.

78. V. Ulianin, ON THE DEVELOPMENT AND REPRODUCTION OF DOLIOLUM (Moscow, 1882), 100 pp. B. Uljanin, DIE ARTEN DER GATTUNG DOLIOLUM IM GOLFE VON NEAPEL UND DEN ANGRENZENDEN MEERABSCHNITTEN, FAUNA UND FLORA D. GOLFES V. NEAPEL, X. Monographie (1884), 140 pp.

The article in which this discovery was published possesses important significance in the history of doliolum, as it contains the first observations on the development of this animal. Krohn not only described the tailed larva of doliolum, tut he also pointed out the alternation of generations in the reproduction of this animal.... On the basis of his observations Krohn concluded that from the ovum of doliolum is formed the tailed, freely swimming larva, which after the loss of the tail is transformed into an asexual doliolum" (p. 2). Later on Ulianin noticed Krohn's mistake in dividing doliolum according to the number of muscular strips. In all species of sexual generation there are eight, but in asexual species there are nine strips. Therefore the species described by Krohn, Doliolum Trosoheli , is in fact an asexual individual D. dentioulatum Q. and G., and D. Nordmannz Krohn is the asexual generation of D. Mulleri Krohn. Particular significance was given by Ulianin to Krohn's embryological observations. "All that is known presently about the embryological development of Doliolum," Ulianin wrote, "comes exclusively from Krohn, who for the first time described the free larva. All later authors.... only redescribed it, not adding anything essential to Krohn's description (p. 47).

The central place among Krohn's investigations of the development of tunicates is occupied by his work concerning the solitary ascidians.? 9 The artificial insemination in ascidians which was used successfully for the first time by Baer, Krohn also used, observing the development of Phallusia mammillata step by step for three months. He described the mature ovum of this ascidian in the following way. The ovum present in the ovum-fluid is supplied by papillae and covered by a cover membrane under which the proper ovum membrane is present. Somewhat deeper lies a hyaline membrane containing inclusions which is green in color. The yolk itself is colorless, the embryonic vesicle and the embryonic spot in the mature ova are unnoticeable . The above mentioned green hyaline membrane was considered by Krohn, following MilneEdwards, a source of formation of tunica. The error of this view was later established, but it was repeated in many

79. A. Krohn, "fiber die Entwickelung der Ascidien," ARCH.

ANAT., PHYSIOL. (1852), pp. 312 - 333. In the following year this work was published in English as "On the Development of the Ascidians," SC. MEM. NAT. HIST. (1853) , pp. 312 - 329.

subsequent embryological works . The division of the ovum begins two to three hours after contact with the sperm. Krohn considered that the division, at least in the first stages, follows the rule of progress. The vesicular nuclei of the globules of division disappear before every division and then again become visible. "Instead of nuclei," Krohn wrote,

in every divided globule an absolutely peculiar distribution of yolk molecules is noticed. Namely, they are distributed in the form of strands, which are directed from the depth, from the medial point by radius in all directions to the lighter periphery of the ovum and, apparently, come out from two centers of irradiation. After the end of division, inside the new globules the nuclei again become noticeable, then these radiant figures disappear and the yolk granules are found to be situated close to each other, (p. 315)

These observations show that Krohn exactly described many details of mitotic division in blastomeres.

Embryonic development goes quickly, and a day after fertilization a cercaria-like embryo with a more or less developed tail is already present in the ovum membrane. The body and the tail of the embryo are composed of cells which are especially noticeable on the surface. The cells have a polygonal form, and contain granules and nuclei in the center. The axis of the tail, according to Krohn 1 s description, is composed of larger rectangular cells with nuclei situated in a row, one following the other, and therefore they have a striated or a disjointed form (Figure 48, A, b) .

Shortly before the final formation of the larva the tail undergoes remarkable transformations. According to Krohn' s observations, they amount to the following. The axis is transformed into a canal, as its cellular structure gradually disappears due to the destruction of the partitions between the neighboring cells and the liquefaction of their contents. The small cells surrounding the central tail strand are transformed into longitudinal muscular fibers. On the dorsal side of the larva at first appears one, and then behind it another, pigmented spot of granular origin (Figure 48, A, d, e and B, e, f ) . At the time of transformation this formation is destroyed, and the pigment passes into the blood channel. The formed larva is set free from the membrane by the tail movement. The body of the larva CFigure 48, B) in the anterior end is supplied by three similar processes on the sucker. The larva is soon attached at the anterior end and undergoes transformation, one of its marks being the disappearance of the tail. Milne-Edwards saw only that the axial part of the tail is set free from its covered sheath and extends into the body of the larva, but he did not elucidate the subsequent fate of this formation. "By my observations," Krohn noted,

the setting free and the extension of the tail axis , the deep immersion by the tail in the body of the larva only precedes the processes of reduction which it soon undergoes. Directly after the extension, the tail axis remains undamaged at the posterior part of the body. It is situated here convoluted into a spiral coil . . . . With the beginning of the development of the young ascidian, this coil first disintegrates into a large number of strips situated close to each other, which then are gradually destroyed; the number and size of the strips decrease, but the insignificant remnant does not disappear entirely. (Figure 48, C) (pp. 318 319)

Krohn himself considered his observations on the development of ascidians incomplete, and he acknowledged only the most essential changes. He described in particular the formation of the vessels of the tunica and the development of the respiratory cavity, or gill cleft, and behind it the rudiment of the digestive canal in the form of a loop-shaped canal . Somewhat later three openings on the spinal side of the body appear: the most anterior, the inlet into the respiratory cavity and digestive canal, and two posterior which later merge together in a common excretory opening. Simultaneously, the nerve ganglia develop in an elongated formation in the middle of the back near both pigmentation spots. Near the nerve ganglia the rudiment of the muscular strands form and the dorsal fissure appears. The digestive canal is differentiated into three parts: a canal which opens into the respiratory cavity, stomach, and intestine. In the walls of the respiratory cavity there develop near the stomach the first branchial clefts with cilia at the edges, and at the ventral fissure the heart develops, possessing the form of a short duct. The metamorphosis is completed by the specialization of the gill-clefts and the development of siphons .

Figure 47. Larvae of Doliolum Nordmanni .

A — Larva up to transformation: a — larval membrane; b— young doliolum; e, f — posterior and anterior opening; d — axis of the tail; B — larva of doliolum in the beginning of transformation: a, d, e, f — as in A; c — "vesicular appendix; g— wall of the respiratory cavity; h — -digestive tract; k — stomach; 1 — intestine; m — heart; n— ventral fissure; o — nervous ganglion with outgoing nerves; p—— the third from back muscular strand, penetrating the rudiment of the stolon (q) (by Krohn) .

Krohn's work represents the first systematic description of ascidian development in world literature; it remains incomplete and not free from mistakes, which, of course, does not reduce the historical significance of this undoubtedlyremarkable investigation. But the exact and detailed study of the embryology of ascidians belongs to A. 0. Kovalevsky. In his work, their relationship to the vertebrates was proved, delivering a fatal blow to the metaphysical theory of types in the animal kingdom. It formed the basis of comparative evolutionary embryology, first advanced by Krohn. In the work dedicated to the development of ascidians, 80 Kovalevsky wrote the following:

Leaving aside the investigations of earlier authors, whose results either are already completely reworked by present scientists, or, to a lesser extent, are partially expanded, we must mention Milne-Edwards, Van Beneden, Kolliker, and, in particular, Krohn. Of all these investigations the results of Krohn's investigations are in closest agreement with our own results. Although he described the accumulation of pigments, which completely coincides with our observations , he did not discover the walls of the saccule in which these organs of sensation are situated, and generally he traced the development step by step. The formation of the axial strand in the tail of the ascidian larva was observed by Krohn, although he explained it as a formation of emptiness in the cells . Although the transformation of the larva into the sessile form was described by him in detail, he had only a slight understanding of the anatomy of the larva and therefore he could not observe the particular features, (p. 41)

80. A. O. Kovalevsky, "Istoriya razvitiga prostykh astsidii"

(The history of development of the simple ascidia) (1886) , SELECTED WORKS (Izd. AN SSSR, 1951) , pp. 41 - 78.

81. A. Krohn, "Uber die fruheste Bildung der Botryllusstocke," ARCH. NATURG., 35 (1869), pp. 190 - 196; Uber die Fortpflanzungsverhaltnisse bei den Botrylliden, " ibid ., pp. 326 - 333.

At the end of the 1860s, in Naples, Krohn studied budding in the complex ascidian Botryllus , and he presented the results of his observations in two reports. 81 In the first of these articles Krohn disproved the erroneous data of Milne-Edwards and Sars and confirmed the observations of Mechnikov that the larva of Botryllus possesses the same simple structure as that of the solitary ascidian and undergoes analogical metamorphosis. After settling on the bottom, the young Botryllus , already in the process of transformation, produces a bud from which a second individual originates, which in turn begins to bud. As a result a stellate colony is obtained. The budding of the colonial ascidian is represented in the second article, in which Krohn compared its details with the corresponding phenomena in salpa.

With these fragmentary investigations of vegetative multiplication, Krohn' s scientific activity apparently came to an end. In the following years (1870 to 1880) his reports were regularly placed in journals, but no works appeared after this time.

For thirty-five years he collected facts from the field of anatomy and embryology, mainly of invertebrates, covering a very great number of systematic groups CI 40) . His embryological works (including descriptions of larvae and means of reproduction) concerned coelenterates, nemerteans, annelids, molluscs, crustaceans, echinoderms, and tunicates.

Krohn did not belong to those investigators paving new roads in science. All his comparative-anatomical and comparativeerabryological remarks are concerned with the comparison of closely related forms. Comparing, for example, representatives of different classes of echinoderms and establishing the features of similarity and difference between salpa and ascidians, Krohn did not offer sympathy either to the theory of types, nor to the idea of unity of planes, nor to evolutionary study. Krohn cited Darwin only in his works on the structure and development of cirripedes, highly rating his monograph dedicated to this order of crustacean.

Besides this, evidence exists about Krohn' s deep interest in the investigations of A. 0. Kovalevsky, who established the similarity of the embryonic development of ascidians and vertebrates. The first report by Kovalevsky dedicated to the development of ascidians was published in 1866 in ZAPISKAKH PETERBURGSKOI AKADEMII NAUK (Notes of the Petersburg

Figure 48. The development of the ascidian Phallusia mammillata (by Krohn) .

A — late embryo with two pigmentation spots: a — body;

b — beginning of the tail; c — rudiment of upper sucking processes? d, e — anterior and posterior pigmentation spots .

B — larva, side view: a— tunica with green bodies; bb— the axis of the tail; cc — its canal; d — horizontal half; e, f — anterior and posterior pigmentation spots; g — right anterior; h — posterior sucking processes.

C — Phallusia in the process of metamorphosis: a— widely opened respiratory siphon; bb— posterior (constrictor) siphons; c — nervous ganglion with the nervous branches; d: — digestive tract; e — stomach; f — intestine; g — situating coil of the larval tail; hhhh — first two pairs of gill openings of the respiratory sac; i — pigmentation mass over the nervous ganglion; k — ventral fissure; 1, 1 — tunica.

Academy of Science); two years later an article followed in NACHRICHTEN VON DER GESELLSCHAFT ZU GOTTINGEN. The data mentioned there, apparently, did not convince Krohn. In 1871 in ARCHIV FUR MIKROSKOPISCHE ANATOMIE, edited by Max Schultze, a new work by Kovalevsky was published, 82 a t which time Schultze added the following postscript to a letter directed to Kovalevsky on January 18,1871: "Krohn, who read your article in proof and made minor corrections, sends you heartfelt regards. At first he was, as you can imagine, very much against the relationship with vertebrates; 83 b u t then he began to hesitate." 84

Krohn was one of the pioneers of zoological investigations on the Mediterranean coast, which later became a place of pilgrimage for naturalists from different countries of Europe.

It is highly probable that Kovalevsky and Mechnikov were well acquainted with the works of Krohn. His remarkable comparative embryological investigations, of which they became aware in the mid-1860s, revealed the nature of Krohn 1 s scientific activity and produced an impression on them. Like Krohn, they spent many years of their lives as travelling naturalists, more than once following him to those localities

82. A. O. Kovalevsky, "Entwickelungsgeschichte der einfachen Ascidien," MEM. AC. SC . ST. PETERSB . , VII Ser., 10, No. 15 (1866), 16 pp.? "Beitrag zur Entwickelungsgeschichte der Tunicaten," NACHRICHTEN VON DER GESELLSCHAFT ZU GOTTINGEN, No. 19 (1868), pp. 401 - 415? "weitere Studien iiber die Entwickelung der einfachen Ascidien," ARCH. MIKR. ANAT., 7 (1871), pp. 101 - 130.

The Russian translation of the first and third articles are to be found in A. O. Kovalevsky, SELECTED WORKS, editor and commentator A. D. Nekrasov and N. M. Artemov (Izd. AN SSSR, 1951), pp. 41 - 78 and 79 - 122.

83. The paper was on the relationship of ascidians to vertebrates .

84. Schultze' s letter is included in the book PEREPISKA A. 0. I V. 0. KOVALEVSKY (Postscripts of A. O. and V. O. Kovalevsky) , edited by A. A. Borisiak and

S. Ya. Streich. The extract of this letter is published here with the permission of S. Ya. Streich.

rich in the zoological material of the sea — Naples, Messina, Nice, Madeira — and using, in particular, those subjects on which Krohn made many important observations leading to serious theoretical meditation. Kovalevsky later cited with respect the works of Krohn on the structure of sagitta and the development of tunicates, and Mechnikov cited his works on the development of coelenterates and echinoderms .

In the preparation of that revolution in embryology which was accomplished by Kovalevsky and Mechnikov, converting the comparative-descriptive embryology into comparative evolutionary embryology, Krohn 's modest investigations played their role, and therefore his name must not be forgotten in the history of Russian science.

Comments

(1) Needham arbitrarily limited the contents of his book absolutely to the history of chemical embryology. In addition, his extreme unobjectivity drew attention, as he dwelt mainly on the works of English authors, while, according to his opinion, the book should have represented the history of embryology of all times and peoples. In the chronological table of scientists of the world embryology, covering up to the beginning of the 20th century (p. 266 of Russian translation) , Needham did not find places for the names of N. A. Warnek, A. 0. Kovalevsky, I. I. Mechnikov and their numerous Russian followers in contrast to

Fr. Balfur, who published more than 70 years ago the first (and for that time excellent) manual book on comparative embryology, in which the Russian works were given proper places (14) .

(2) Samples of these "compositions" are pictured on the prints of that time, reprinted in the book "Kunstkamera Peterbergskoi Akademii Nauk", 1853, 293 p. (see Fig. 6.10 and 11 of the mentioned book) . Description of anatomical and embryological "compositions of Ryuish and texts of the poetical Latin inscriptions which accompanied them much earlier were mentioned by Baer in "Memories about anatomical cabinet" ("Memoire uber das Anatomische Kabinet, gelesen in den Sitzungen der Phys.-math. Kl. d, Sep. 20, 4 u. Oct. 18, 1850; Collection the museum of anthropology and ethnography in Imp. Ac. Sc, 1900, p. 111-152) (21).

Here and below figures in round brackets show the number of text page, to which the comment is related.

(3) Doctor van der Hulst, (see below for data about him) on April 14, 1724 ,; sent organs which belonged to a girl, who died of smallpox, in Kunstkamera. Caesar honored him due to the hermaphrodite (Materials for history of Imp. Ac. Sc, V. 1 Spb, 1855, p. 38) in the other place of these "Materials" wrote due to bringing to the Academy of Science a monster, who was born with two heads, determined by Doctor Stepan Gaokantsk, ...8 roubles were given" (V. II, on March 9, 1732, p. 119) (23).

(4) In "Materials for history of Imp. Ac. Sc." there are many documents about the obtaining of teratological objects into Kunstkamera.

A letter from Vyborkh by colonel general Karnov says "his major Beshentsev Fedor Fedrov in the Vyborgskaya office found a monster of a lamb having four legs and one neck, and the head had the view of a double one. This head had two mouths with tongues and two eyes: they were in the

middle where the forehead must have been " ('Materials..

V. I, Spb., 1855 No. 165, March 9, 1725, pp. 9-97).

Inventory of objects, obtained on March 8, 1725 "Number 1: lamb, with 8 legs, another with three eyes, two trunks, 6 limbs were sent from Tobol'sk by Kozlovsky. Number 2: baby, with 3 legs: from Lower Novgorod from Governor Rzhevsky. Number 3: calf with 2 deformed legs: from Ufa from commandant Bakhmetov. Number 4: baby with two heads also from Bakhmetov. Number 5: one baby, with eyes under the nose and ears under neck: from Nezhin. Number 6 - two babies - breasts and abdomens were joined from Akhtyrok from prince Mikhail Golitsyn; hands, legs and head were normal. Number 7 - baby, with a fish tail, born in Moscow in Tverskaya. Number 8: two puppies, born from a 60-year-old woman, from Akhtyrok from prince Golitsyn. Number 9: baby with 2 heads, 4 hands, 3 legs: from Ufa from commandant Bakhmetov" ("Materials...", V. I, No. 193, March 18, 1625, p. 99).

Grigorii Ivanov found a monstrous head puppy with 8 legs ("Materials, V. I, No. 291, September 21, 1725, p. 145).

"....Dead body of an infant, with 6 fingers, horn by a daughter of Tikhanov who was working on a marine ship Astrakhan. . .given in Kunstkamera" ("Materials..." V. II, 1886, No. 99, November 29, 1731, p. 83).

"On January 17 of this same year, my brother sent a monster which had 2 mouths, the daughter of Ulita Kiryanova the wife of sergeant Nikivor Kosharov gave birth to it: this monster had four hands, four legs and two faces, one had normal view and the other had one eye" ("Materials...", V. Ill, 1886, No. 13, January 20, 1736, p. 14).

"This monster was accepted for preservation in Kunstkamera and Kosharov was given 4 roubles as a reward" (there is also, No. 41, February 17, p. 36) (23).

(5) Iogani-Georg Dyuvernua (1691-1759) a Russian

academician in the department of zoology and anatomy, was invited to the academy during its foundation. In 1741, by efforts of Shumakher, he was compelled to leave work and travel to his homeland, in Germany. Following him, up to 1758 Abraham Kaau-Boerhave (1715-1758) had been in charge the department of anatomy and physiology in the Academy of Science. In his era, the anatomical and embryological collections of the academy came into being, but he practically did not use them. He published one of them in detail (Abraham Kaau-Boerhave was related to those foreigners, living in Russia, who did not make anything for promoting its sciences and for preparing the young Russian scientists (23) .

(6) Family of van der Hulst was repeatedly mentioned in the documents of Petrovskaya epoch. Doctor Zakharii van der Hulst arrived in Moscow from Holland, apparently in the 70s of the 17th century, and for a long time he was the physician of Aptekarsky department and court physician at tsars Ivan and Petr. Then after the death of Ivan, he became the physician of Petr I. He accompanied him on both journeys to Arkhangelsk (1693 and 1694). On the second Journey, he die-' suddenly* . Another van der Hulst

V. Rikhter. "Istoriya meditsiny v Rossii" (History of Medicine in Russia), p. 2, Moscow, 1820, p. 313, M. M. Bogoslovskii, Petr I, V. I, p. 181= V. II, 1941, pp. 123-124.

participated in 1691 in Poteshny battles" in the army "generalissimusa" of I. I. Buturlin 2 . In 1695 in "Rospisi nachalnym lyudam Semenovskogo polky" captain Andrei Yakovlevich van der Hulst was mentioned^. On the first journey of Petr to Holland, at the Russian Embassy, lieutenant (or captain) Andrei (Yakovlevich) van der Hulst 4 became the translator. One year later, t he was sent by the Dutch government to Moscow as resident* Later on, the son of the above mentioned "doctor" Zakharii van der Hulst— Zakhar Zakharovich— was known. By the order of Peter I, he received "traveller sheet" via Mozhaisk, Vyazm, Dorogobuzh and Smolensk in foreign lands for studying science. Although it was impossible to detect exactly the time of his return to Russia, but there was no doubt about it . He was a teacher of surgery at Peterburgsky Hospital 1723 6 . Ya. Chistovich informed, that "Z. Z. van der Hulst passed the Doctorate degree examination in Leiden and after returning to Russia he was the senior doctor in Petersburg Admiral Hospital and, in addition, a teacher for medical students and pupils of this hospital. Later on, he lived in Moscow and when a "Doctor's committee"? (1730) which comprised five doctors was established, he was one of its members. It is most

2. There also, V. I, p. 127.

3. "Sb. vypisok iz arkhivnykh bumag petre Velikom" (Collection from archives papers about Petr the

Great) , VI, Moscow, 1872, p. 148.

4. M. M. Bogoslovskii. Petr I, V. II, p. 155, 182, 421.

5. There also, V. II, p. 432> V: IV, 1948, p. 252, 339, 340, 344, 346.. M. A. Venevitinov. "Russkie v Gollandii. Velikoe posol'stvo 1691-1690 godov" (Russians in Holland. The great embassy 1697-1698) Moscow, 1897, p. 79.

6. V. Rikhter, Istoriya meditsiny v Rossii, p. 3, 1820, p. 149.

7. Ya. Chistovich. "Istoriya pervykh meditsinskikh shkol v Rossii" (History of first medical schools in Russia) . Appendix X. Alphabetical list of doctors of medicine, working in Russia in the 18th century.

probable, that Zakhar Zakharovich van der Hulst is the author of a dissertation cited in the text on page 7: the difference of names (Zakharii and Arnold) does not speak against this supposition, as both names could belong to the same person. Anyhow there is no doubt about the belonging of the author of dissertation to the Moscow family of van der Hulst (25) .

(7) Speaking about the collection of anatomical preparations, present in Kunstkamera N. G. Kurganov noticed, that

"the greatest attention was given to these parts, which explained parturition. A number of the foeti exceeded more than one hundred and composed a gradualness from an embryo having the size of an anisic grain to a completely formed baby. The collection of monsters was extremely big. These anatomical descriptions with sketches, reprinted on copper, had a scientific significance" ("Pismovnik", the second part, p. 196) (32) .

(8) In chapter 26, "Gippokratovskoi sbnornik" it is possible to read the following: "All organs are distinguished simultaneously and they grow, and not one is distinguished earlier than the other. But the larger ones in nature are distinguished before the smaller ones, not originating in any case earlier. However not all receive the final structure

in equal time, but some are quicker, others are slower, since each meets sufficient nutrition. In some, all become distinct within 40 days in others — within 2 months, in others — within 3 months, and in others — within 4 months" (See V. I. Karnov. Aristotle i antichnaya embriologiya. Introductory article in the translation of Aristotle" "0 vozniknovenii zhivotnykh" Izd. AN SSSR, 1949, p. 23 (35).

(9) The embryological opinions of Dekart are stated

in the treatise "Opisanie chelovecheskogo telo" (Description of human body) , where they compose its fourth part — "About the development of the embryo. Parts, formed in semen" and the fifth part "the formation of hard parts". The treatise was published two years before the death of the philosopher, in 1648. In addition, with the birth conception of living substances, "which are produced by semen", Dekart also assumed the possibility of spontaneous conception (without semen and uterus") . *

In case of conception from parents, their semen is mixed and forms cloudy liquid which undergoes a kind of fermentation, what is formed during this heat widens the particles of semen, they "press on other particles subsequently locating them gradually. This is the way of forming the body organs... Heat compels some of the particles of semen to be collected near definite points of the space... Thus the heart begins to be formed"2. The movement of blood from heart makes a way through semen particles, that is why the blood again returns to the heart, and by this way the vascular system is formed. After this, the movement of particles of different kinds leads to the subsequent formation of the organs - vertebrates with spinal cord, brain, paired organs of sensation and so on. The energetic character of these embryological presentations is completely obvious. However, Dekart considered that it is necessary to underline this. "In order to get acquainted with the figure of the already formed animal, it should be understood what it represents at the beginning of its formation and it is necessary to imagine semen, as some mass, from which, the heart is first formed, around it the hollow vein is located on one side while on the other the large artery, united by two tips. The tips of these vessels, to which the openings of the heart are directed, indicate the side, where the head must be present, others also indicate that side, where the lower parts of the body must be present" 3 (36) .

(10) The idea of preformation may be traced back to remote ancient times. Anaksagor taught that "hairs cannot be formed from no hairs and raft from no raft" similar ideas were stated by several authors especially Senekoi, who in "Questions of nature" wrote: "In semen all future

1. See S. F. Vasilev. "Evolution ideas in Dekart philosophy (Introductory article in book" Rene Dekart. Kosmogoniya . Two treatises. GTTI. 1934, p. 121) .

2. R. Dekart. Description of human body. In book: Kosmogoniya, p. 286-287.

3. See also pp. 298-299.

parts of the human body are contained. The baby in the uterus of the mother has already roots of beard and hair, which he will carry. In a similar way, in this small mass, are contained all features of the body as well as all those, which will be present in his posterity" (see Dzh. Needham, History of Embryology, page 76) (37) .

(11) The theory of "investment", conformable to plants and animals, was stated by Mal'bransh in the following expressions: "It seems, although it may be a hardlyaccepted idea, that in one embryo a countless number of trees is included, because this embryo does not include only a tree, serving as its seed, but also, great number of seeds, which can include new trees and new seeds of trees, containing, in turn, probably in an incomprehensible little form, other trees and other seeds, are fruit bearing as the first and so on till infinity. All what is mentioned about plants and embryos can be also applied on animals and their embryos, from which they were produced. In the embryo of a bulb of tulip, it is possible to distinguish all tulips. Thus in the embryo of a fresh non-hatching egg as well, it is possible to see a chick, which may be nearly completely formed. In the eggs of frogs, it is easy to recognize frogs, we will also find other animals in their embryo when we become so experienced and skilful, that we can open them (N. Mal'bransh. "seeking out truth" translated by E. B. Smelovaya, V. I, 1903, p. 51-52) (38) .

(12). Speaking of the influence of the mother's impression on the formation of fetus, Mal'bransh, among other examples, mentions the following: "One year did not elapse still from that time, when a woman, looking with great zeal on the picture of Saint Pia at the time of the celebration of his canonization, delivered a child, absolutely like the Saint He had senile face, which was impossible for a child, but did not possess a beard. His hands were put together as cross on the chest, his eyes were directed to the sky. He had a very small forehead, because on the picture, the image of this Saint was raised to the dome of the church, directed to the sky, so that his forehead was nearly unnoticed. On his shoulders, he had something like overturned mitre with some round birth marks, at these places where mitres were decorated with precious stones. In short, this infant extremely resembled the picture, but his form was made by the strong imagination of his mother. All Paris could see him, as I could, because this infant was preserved for a long time in spirits of wine" (N. Mal'bransh. Seeking out truth, V. I, p. 173).

The description of deformity was so expressive and exact, that confidently it was sufficiently possible to characterize it in terms of recent teratology. Probably, the matter was a case of amencephaly or, may be, cerebral hernia of occipital region. It is not wonderful that the baby, resembling Saint Pia, was shown in a jar with spirit directly after bith (38) .

(13) Philosophy, Leibnits spoke, - gave itself much work about the origin of forms, entelechy and soul. Meanwhile, different accurate investigations, performed on plants, insects and animals, led to this conclusion: that the organic bodies of nature never originated from chaos or not, but always from semen, in which, undoubtedly, preformation was already present... We see something similar, when, for example, worms become flies and caterpillars become butterflies" (Monadologiya, No. 74), (38).

(14) "Thus, I suppose that souls which once must become human souls, as well as souls of other kinds, existed in semen, in ancestors up to Adam, i.e. from the very beginning of things they existed in the form of organic bodies — a view, which was apparently approved by Swammerdam, Mal'bransh, Beil', Pitkari, Gartsuker and many other learned men. This view is also sufficiently confirmed by microscopic observations of Leeuwenhoek and other fairly prominent naturalists "(Teoditseya, I, No. 91) (38).

(15) Leibnits considered that monads are alive and animated, characterized by incessant change which is accomplished continuously without leaps. "I confirm, as an indisputable truth — he wrote — that all things were exposed to change, and became monads and that in each monad this change was accomplished continuously" (Monadologiya, No. 10) . From continuous change, the developing monad natural passage of Leibnits to gradation of monads, forming continuous eternal ascending series of substances, progressing from unaccomplished to accomplished. By his investigations "Swammerdam showed that insects, by their respiratory organs, are similar to plants, and that in nature, an order of gradualness, descending from animals to plants, exists. However, there may be, in addition, intermediate substances between these and others" (Letter of Leibnitz to Bung). And in another letter: "I am sure, that these substances must be present, and natural science may discover them. Nature never disturbs continuity anywhere. It does not make leaps. All categories of substances of nature form one sole chain, where different classes, like links, so closely join to each other that for sensual presentation it is impossible to determine the point, where each of them begins or ends" (cited by Kuno Fisher) ("History of new philosophy, V. Lebnitz", p. 460) (38) .

(16) About this change of his opinions, Haller wrote the following: "In the body of animal, there is no part which can originate earlier than the other: all of them are formed at the same time... If Harvey supposed that

he discovered the epigenetical development, it is because from the beginning he only saw small haziness and then the rudiments of the head and eyes, exceeding in size all other bodies, and finally gradually — the internal organs. More than 20 years ago, i.e. before my numerous observations on eggs and females of Tetrapoda, I used this argument to prove that embryo strongly differed from the formed animal, while I confirmed, that in animals at the moment of conception parts which were present in completely formed animal were absent. From this time, I had the complete possibility to confirm that all that was deduced by me against preformation theory, in fact speaks in its favor" (cited by Dzh. Needham, History of Embryology, p. 226-227) (39).

(17) On the basis of the confirmation of the Bible, that earth and mankind populating it, have existed about 6000 years and from that the average duration of life of

man is equal to 30 years, Haller calculated, that God created at the same time a minimum of 2000,000,000,000 people (cited by article of Kirchhoff on Wolff, p. 204) (39) .

(18) Speaking about the impression produced on contemporaries by the discovery of Bfennet (about the development of bodies from unfertilized ovum), A. E. Gaisinovich noticed that the scientists of that time... lost sight of that it proved in the best case only ovism but not preformation (Cited article in the edition of translation "Theory of conception" of Wolff, 1950, p. 379). With the latter confirmation, it is difficult to agree: ovism is one of two forms of the preformation theory and is principally identical with its other form — animalculism. (40)

(19) After that the chapters of this book, dedicated by Wolff, were written, he mentioned in the preface "Theory of conception" of Wolff (Publisher House Ac. Sc. USSR, 1950) which was published with the supplement of article A. E. Gaisinovich "K. F. Wolff and studies on development" (pp. 363-477) Tasks, which the author of this interesting article put before himself, did not allow him, apparently, to stop and dwell in more detail on embryological and teratological works of Wolff.

Here it is also necessary to notice that the translation replaced in the Russian edition of Wolff the term "generation" by the word "conception", which could not be considered felicitous. The term "conception" meant the beginning stage of development, appearance of a new individual, while Wolff did not mean only this stage, but also all subsequent individual development. It is completely accurate to translate "generation" by the word "development". Wolff himself used in his German book neither the term "conception" (Entstehung) nor the term "development" (Entwickelung) , and dept the Latin root in the German word "die Generation". In accordance with this, upon the examination of Wolff's dissertation and its popular summary in German below the original Wolff term "generation" is preserved (43) .

(20) In the first volume of "Zur Morphologie" Gete mentioned Wolff in four places. He gave a brief account of biography of Wolff (p. 80-83), mentioned in the notes of Murzinitsa on Wolff (p. 252-256), then dwelt on studies of Wolff about metamorphosis of plants (p. 83-87) . At last he tackled the understanding of educational yearning, using the terms of Blumenbakh (pp. 114-116).

In the last extract Gete writes the following "In criticism of ability to reach an opinion" Kant states "In relation to the theory of epigensis no one worked either for its proof and for substantiation of true principles of its application, or partly for the restriction of its extremely wide application, as Mr. Buildings advisor Blumenbakh". This evidence of honest Kant encouraged me again to scrutinize work of Blumenbakh, which I truly read before, but did not imbue it. Here I found my Christof (1-L.B.) Friedrich Wolff as an intermediate link between Haller and Bonnet; on the one hand, and Blumenbakh, on the other. For his epigenesis, Wolff must suppose the presence of an organic element, on which creatures feed, which is intended for organic life, and supplied this material by an essential force". The mentioned words of Gete witness to the superficial acquaintance of the great poet with the views of Wolff (Even Wolff's name was written incorrectly by Gete (44) .

(21) A. E. Gaisinovich (1950, p. 462-463) mentioned information, that Wolff at the beginning of the 70th year taught in the academic high school— chemistry, anatomy and botany, and he also directed the preparation of the scientific activity of student Fedor Galchenkov (48) .

(22) This place in the translation of Meckel tendentiously stated: instead of "the Highest Creator" was put "The creating nature". Wolff disputed the preformation of formulated parts; in the German translation, his skepticism is not related to the Creator for the authority is untouched, but to nature. This "liberty of translation" bars the radicality of scientific and philosophical view of Wolff (76) .

(23) Here the phrase made by Wolff, has no connection with other discussions and clearly intended for not blaming atheism: eiusmodi vero materia, talibus, viribus instructa immediate a Deo ex nihilo creata sit (it is also true that material, supplied by these forces, is directly created by God from nothingness) (76) .

(24) A. E. Gaisinovich (1950, p. 455) repeated the mentioned statement of K. M. Baer nearly literally: "This remarkable work of Wolff... did not draw the attention of all the scientific world up to 1812, when Meckel translated it from the Latin language". It is necessary to notice, however, that the work of Wolff was given due attention and it was evaluated as a remarkable work in the book of I. Bezeke, published in 1797 (see p. 114) and in the dissertation L. Tredern (1808) (see Chapter 11) (87) .

(25) Apparently, in the declaration of biological works by the Academy of Science for a prize, Wolff showed initiatives also early. Thus, in 1779 the academy declared a competition for a prize on the question about reproduction of cryptogamous plants. This theme of competitive work

was written in expressions which a great probability impel to consider Wolff the author of this question: "Theoriam generationis et fructificationis plantarum cryptogamicarum Linnaei dare etc...." (gives the theory of development and fruiting of cryptogamous plants, by system of Linnae, plants and so on) .

In 1783, this prize was awarded to a professor in Leipzig, log. Gedvig for the work under the title "Theoria generationis et fructificationis plantarum cryptogamicarum Lennaei, mere propriis observationibus et experimentis superstructa dessertatio, quae praemio ab. Academia imp. Petropol. pro Anno MDCCLXXXIII proposito ornata est" (105).

(26) It is necessary to notice, that the embryological problems have interested Petersburg Academy of Science before the arrival of Wolff. It is possible to judge this, in particular, by the published collection in 1756, which is composed of two works (dissertations) , and sent to the competition announced by the academy. The question, put by the academy, touched upon the possible influence of the impression, felt by the pregnant woman, on the developing fetus. One of the mentioned works belonged to a professor

at Leipzig University C. Ch. Krauze*, and another — to a member of Petersburg Academy of Science, I. G. Rederer. In lively controversy on this theme Byuffon participated. He energetically objected to preformists, who according to their views, the embryo is proved to be similar with the parents under the influence of imagination of the mother.

Caroli Christiani Krauze. Dissertatio de questione ab Academia imp. scientianim petropolitana pro praemis in annum MOCCLVI proposita. Quaenam sit causa proxima mutans, corpus foetus etc... There also, J. D. Roederer Dessertatis Petropoli 1956.

In the controversy Terner also participated. He objected to Blondel, denying the influence of mother imagination on the embryos. Argument of Terner was confirmed by the fact that the blood vessels of the mother directly passes in the vessels of the fetus. Ens subscribed to Terner' s opinion. Apparently, the difference, existing on this question in literature, induced Petersburg Academy of Science to announce competition on works which would comprehensively answer it. The scientific committee of the Academy, examining the competitive works, revealed scientific impartiality, and the Academy published two works, each one of them represented a contradictory opinion. Krauze was a supporter, and Rederer was an opponent of the influence of maternal imagination on the fetus.

Krauze considered that the question raised was very difficult, nearly hopeless to solve. However, he noticed, that many examples were present, when the fetus was changed in a way, that not only simple people and the mother herself, but even sharply sensitive scientific people in medical practice related it, although partially, to the strong emotional shock of the mother. Enumerating the opinions of authors, discussing this question (Sennert, Morisso, Ludvig, Hofman, Abraham Kau-burgav, Takhoni and others), Krauze suggested, that the reader can make for himself the most classical ironical defiance: "Hie Rhodus, hie salta!" (literally: "Here Rodos also jump!") and all the following statements attempt to answer this call. As also the majority of his predecessors, Krauze paid attention mainly to cases of appearance of pigmental birth marks, where their forms and situation compel to suggest the influence of pregnant women. He began with these sharp effects, as terror, fear, anger and so on, showing strong physiological influence expressed first of all in the reaction from the side of vascular and nervous systems. From this Krauze made the conclusion, that "if the brain was strongly alarmed, then small changes took place in the body". Referring to known cases of adult people suddently growing grey under the effect of deep feelings, Krauze suggested that, there were more bases to expect changes of skin color of the fetus under the effect of maternal imagination. If terror or fear can cause small ulcers on lips or erysipelas, then why does it seem incredible to you, that the same phenomena can take place in the body of the fetus, whose structure is so weak and delicate, and its vessels are so numerous and full of juices?"

611

In order to imagine the possibility of this phenomenon, which is shown by the influence of changes in the organism of the mother on the fetus, it is necessary to prove their close relation. On his side Krauze confirmed, "fetus with the uterus represents a single continuous whole". According to this opinion, this is especially related to the nervous system, so that "stimulation of the nerves of the uterus may and must be passed to all the nervous system of the fetus. Distributing this confirmation on psychics, as well as suggesting, that the fetus was capable of psycological manifestations, Krauze deduced the following conclusion: "In the brain of the fetus exists the same condition, which exists in the brain of the mother". All these views are summarized in the concluding paragraph of the dissertation". What was stated so far may be added to all these examples, which instruct, that the fetus body is changed from the mother, if her soul is strongly shocked. Ideas, originating in the mother's brain are "united with fetus brain"; they are stimulated in it more quickly and energetically, than in the soul of the mother herself, as the pulse of arteries and effect of nervous and generally all responses in babies are quicker than in adults. Under the influence of these ideas, the fetus brain gives effect on its body and namely in this way, which corresponds to perceived ideas. Therefore, the fetus's brain produces in the corresponding parts of his body the same things which he himself undergoes".

Directly after the considered work of Krauze, it is necessary to examine the work of Rederer, which is simply entitled "Dissertatis" and also begins with the formulation of the question raised by the Academy: "What is the direct cause for changing the fetus body?..."

In order to possibly answer this stated question, Rederer considered that it is necessary to study thoroughly, how the mother's body unites with the embryo, taking into consideration, that the only connection between them is carried out through the placenta. The investigation of this connection led him to the following conclusion. The lumens of the blood vessels of the placenta, directed to the uterus, up till this stage, are so narrow. They do not admit turpentine oil or any other liquid to pass. True anastomoses, connecting the vessels of the uterus

612

and vessels of placenta, do not exist; Vasa hypogastrica which is full, by all means of a waxen mass or any other fluid, does not pass its contents to the umbilical vessels. This was established either in human carcass, or in living cows, ewes, bitches and other animals. If the pregnant animal is fed on roots of Rabiae tinctorum, then the fetus bones will not be stained with the red color. The blood of the fetus differs from the mother's blood in that it is more liquid. Finally, the fetus pulse also differs from the mother's rate.

Subsequently, the fetus lives its independent life, moving its own blood by its forces, beating of its heart, by blood circulation and through placenta, without the help of the maternal blood. Therefore, rest, movement, sleeping, awakening and even life and death of the mother and fetus are not obligatory present in harmony. Later on, Rederer categorically denied the existence of a nervous connection between the placenta and the mother. The comparison of the positions of the birth marks as well as their presence or absence in the mother and baby does not give, according to his opinion, basis to suggest the influence through blood or nervous system. Rederer discussed in detail the question about "mind" of the fetus and passed to the conclusion, that this mind cannot adequately respond to the feeling of the mother. This is stated by the examples of strong shocks in the mother, not accompanied by the appearance of birth marks in the baby, and examples of appearance of birth marks and warts without any connection with the mother's feeling. In the following pages the various deformities of human beings are mentioned, and Rederer reached the conclusion that the birth marks differ from true deformities only quantitatively. They are also disturbances of the normal development. As the deformities frequently affect the internal organs, then in relation to them, the usual supposition about maternal influence loses its significance. The general conclusion of Rederer comes to that the confirmations about the influence of the mother's feeling on the baby are not supported by verified facts, and are but the product of fantasy (105) .

(27) The effect of vitalistic views of Blumenbackh on some Russian physicians-biologists can be traced up till the 20 's of the 19th century. Thus, in 1825 at Moscow University, the surgeon Nikifor Dmitrievich Lebedev discussed a thesis for the degree of Doctor of Medicine. He later on read at the university "history and literature of medicine". Lebedev dissertation was entitled "About the nature of weightless substances in general and vital powers in particular" (Dissertatio inauguralis physislogica de natura imponderab ilium in genere et de viribus vitalibus in specie, quam...in Universitate caesarea Mosquensi, pro gradu doctoris medicinae. . .elaboravit publiceque defendet chirurgus I-mae classis Nicephorus Lebedev, Mosquae, 1825. 28 p.). Lebedev, referring to Blumenbakh, dwelt on the idea that all vital processes — organic formation and growth as well as movement of already formed parts-possess their own source of a special vital power (55) . The vital power, according to his opinion, is an internal, inherent character in the organic body, which is the cause of life and at the same time seems to be its product (Vis vitalis est interna et proporia organici corpori qualitis, quae vitae causam constituit et simul ejusdem est quasi productum, thesis 9) . Works of similar kind are not characteristic of the common materialistic trend of Russian biological and medical sciences. Therefore, the dissertation of Lebedev served as a reference and mainly as an illustration of this negative influence, which was shown by the idealistic German philosophy and some representatives of Russian sciences especially the naturalists who worked under its direct influence (106) .

(28) Izef Gotlib Kelreiter (1733-1806), botanist and zoologist, worked from 1756 to 1761 as a junior scientific assistant at Petersburg Academy of Sciences, with which he kept in close contact after returning back to Germany and till the end of his life. In the period, from 1758 to 1811, 15 botanical and more than 20 zoological works of Kelreiter were published in Russian scientific and scientific popular editions (Novi Commentarii Acad. Scient. petropolitanae, Acta Acad. Scient. petropol. Nova Acta Ac. Sc. Petropl., Trudy Volnogo Ekonomicheskogo Obshchestva and in the journal "Sochineniya,K poize i uveceleniyu sluzhashchie") . His scientific fame is connected mainly with the study of reproduction and hybridization in plants (see Ioz. Kelreiter" Study about sex and hybridization in the plant", the editor with a biological essay was prof. E. V. Wolff, 1840).

614

The work of Kelreiter about the irritability in the plant, to which Wolff referred, was called: "Nouvelles observations et experiences sur l'irritabilite des etamines de l'epine vinette (Berberis vulgaris)", Traduit de l'allemand par M. I 1 adjoint Sewergin, Nova Acta Acad. Scient. Petropol., 4, 1790 (German original was received in Petersburg in 1788) (112).

(29) The point of view of A. E. Gaisinovich is similar to the presentation mentioned here about the outlook of Wolff (see Wolff "Theory of conception") . It is possible to combine with it the confirmation, that the studies on preformation and epigenesis do not always correspond to the demarcation between idealism and materialism in biology. The following serves as an evidence, that preformists were also idealists (Leibnitz, Haller, Bonnet) and mechanical materialists (for example, Lamettri) ; equally as epigenetics, were either idealists (Aristotle Harvei) ,

or mechanical materialists (Dekart, Maupertuis, Byuffon and Didar3t).A. E. Gaisinovich included Wolff as well in the latter category. His "absolute epigenesis" was grouped together with Gaisinovich in the mechanical materialism. For its complete verification, this statement could be desired as only a less categorical expression. In the evaluation of Wolff's outlook, it is impossible, apparently, to deny absolutely his fluctuations between materialism and idealism; these fluctuations were an unavoidable originality even by the most prominent thinkers of all historical epochs, preceding the formation of successive system, i.e. dialectic system and materialism (119) .

(30) Semen Gerasimovich Zybelin (1735-1802), after finishing the study in Moscow Ecclesiastical Academy, joined Moscow University till the opening there of a medical faculty. After he finished the course, he was sent to study medicine abroad. At Leiden, Zybelin defended a doctor's dissertation in 1764. After returning back to Moscow he read courses of anatomy, physiology, chemistry, pharmacology and therapy as a professor in the mediqal faculty. In 1784, he was elected member of the Academy of Science (121) .

(31) Prince Dmitrii Alekseevich Golitsyn (1731-1803), a prominent Russian diplomat, was a former ambassador in Holland and France, friend of Diderot and Galvetsy, known as author of many physical works (122) .

(32) Dzh. Needham in his "History of Embryology" prefaced the list of the literature sources used by him with a list of works, which he could not obtain. As "less important works on the history of embryology" Needham also mentioned Bezeke's book. It is difficult to decide, on which basis the English historian of embryology considered Bezeke's book less important, if we take into consideration that according to his confession, he never saw it (122) .

(33) Two extracts compose the contents of the already mentioned book of 1797 (in it, as stated, were present an essay on the history of a hypothesis about the conception and development of animals and in addition, "History of the origin of division of the natural bodies into three kingdoms") The third extract appeared in the form of a separate small volume in the year of the author's death (J. M. G. Bezeke. Allgemeine Geschichte der Naturgeschichte in dem Zeitraume von Erschaffung der Welt bis auf das Jahr N. C. G. 1791. Mitau, 1802, XXXII±154S) .

For more details about the works of Bezeke see the article by the author of the present book in "Trudy instituta istoriii estestvoznaniya i tekhniki, V.IV, 1955" (Works of the Institute of History of Natural Sciences and Technique) (123).

(34) Matvei Khristianovich Peken was born in Petersburg, he studied medicine in Ien, where he obtained the degree of Doctor of Medicine (according to other data-- in Gettingen) . When he returned back to Russia he worked as the admiralty doctor, read a course of obstetrics in Petersburg hospitals. From 1793, he travelled to Moscow, where he read pathology and organized the first therapeutic clinic with ten beds (124)

(35) Nestor Maksimovich Maksimovich-Ambodic (1744-1812) finished Kiev Ecclesiastical Academy, studied medicine in Strasburg, where he defended a doctor dissertation about "human liver" (1755). At Petersburg admiralty hospital, he read obstetrics and wrote a lot of works and manual books. The second part of the family (Ambodic) was written by himself in connection with accord of patronymic and family (127) .

616

(36) "Dictionary" of Maksimovich Ambodic is composed of two parts: Russian-Latin-French and Latin- Russian, which was prefaced with 65 pages of the text, explaining the significance of this first Russian terminological dictionary, contents of anatomy and physiology and even some information about these sciences.

In "the foreward to the dictionary in general", Maksimovich-Ambodic writes: "During collection of the words, related to my subject of practice, I have been collecting bees for more than 10 years. The major reason was that the Russian words had been collected from various ancient and recent manuscripts belonging to church and civics."

It is difficult to overestimate the significance of this work as a result of the great quantity of terms created, which were absent in the Russian language. This significance is not diminished by the bulkness of some terms which are not contained in scientific language together with others which are archaic and have disappeared from the language in the process of its evolution.

The historian of national medicine Ya. A. Chistovich drew a special attention to the significance of "the dictionary" of Maksimovich-Ambodic. He noted the unfair relation to Maksimovich on the part of V. M. Richter, who "did not offer him a single line in his biographical History of Medicine in Russia". Fortunately, the voice of this light word was fair and, in defiance of the partial historian, preserved the name of Maksimovich from undeserved oblivion" (Ya. Chistovich. First obstetrician schools in Russia (1754-1785. Essays from history of Russian medical institutions of the 18th century. SPb., 1870, p. 199) (131).

(37) Khristian Elias Genrikh Knakshtedt was born in Braunshveig in 1749, studied surgery in Bryunn and in 1786 travelled to Petersburg, where he was professor of anatomy and surgery at Kalinkinsky hospital. In 1790, due to the work "Beschreibung der trockenen Knochen des menschlichen Korpers" (SPb., 1791) the medical college awarded him the degree of Doctor of Medicine. Knakshtedt died in 1799. In addition to the mentioned works, he also published "Descriptio praeparatorum maximam partem osteologicorum rarissimorum"

617

(Braunschweig, 1785) and Latin-German terminological medical dictionary "Erklarung lateinischen Worter, welche zur Geliederungslehre Physiologie; Wundarzneywissenschaft und... Ordnung" (Braunschw., 1784, 2nd edition, SPb., 1788). In the title page of the latter he called himself Russian surgeon and ordinary teacher of studies about bones and all their diseases at the imperial surgical school in Petersburg.

To the work of Knakshtedt mentioned in the text "Anatomical description of the monster" an invitation to Medico-surgical school is addressed to "all famous persons and members of medico- surgical sciences" to attend the meeting "near Kalinkinsky bridge at Ekateringofskaya and listen to "some works and speeches by some teachers and students. The meeting was proposed to take place on January 7 at 10 a.m. (131) .

(38) Petr Andr^evich Zagorskii (1761-1845) is the one who founded the first Russian anatomical school . After teaching at the Cheringovsky college he went to the hospital school in Petersburg. After he finished there, he worked for three years as prosecutor Petersburg medico-surgical school with professor N. P. Karpinsky. From 1799 to 1833, he was junior assistant, and then professor in medico-surgical school, and from 1805 up to the end of his life he was a member of the Academy of Sciences. Zagorskii organized excellent anatomical museums at the medico-surgical school and Academy of Sciences, published the first Russian manual book on anatomy and a great number of works on anatomy, teratology and different medical topics.

(38a) The same opinion on the origin of monsters was also supported by the academician N. Ya. Ozeretskovskii, who informed the Academy on April 25, 17991 about two cases of double monsters in the preparations of the academic museum of natural history. One of these cases was united twins (union in the region of the upper part of the chest, both partners

1. N. Ozeretskovskii. De doubus foetibus humanis,

monstrosis. Nova Acta Acad. Sc. imp. Petropol., 14. 1805, p. 367-372. The article of Ozeretskovskii was published in the same volume of Nova Acta Academiae Petropolitanae , where the above mentioned report of Zagorskii was also published.

618

were completely formulated) . The second case was the doubling of the head end, beginning from the girdle region; the monster had three correctly- formulated hands, two normal and one underdeveloped legs. The description of the monsters (the first case was illustrated by two excellently-engraved figures, representing the twins from the front and from behind) was concluded with a brief account about the reason for the monsters appearance. By comparison of the described cases, Ozeretskovskii made the conclusion that monsters can be very variable and that each monster, must possess its natural cause. "The physiologists — Ozeretskovskii wrote — must explain these causes and find the specific original source of these monsters — whether their origin is due to the union of two embryos, or from strengthened, weakened or incomplete development of parts of the body" (p. 371).

In another article, whose contents were received by the Academy one year before (on October 25, 1798)1, a description was given for non-hatched hen's egg with an opening in the shell; through this opening the end of a blood vessel passed. When the egg was opened, in addition to yolk and egg white, a pear-shaped body was found in it, which was full of clotted blood. Ozeretskovskii considered the described content in the egg as a polyp of the oviduct, torn at the time of yolk passing, falling in the egg together with the white. In connection with this, he assumed, that the presence of similar kinds of strange bodies in the eggs of birds may be the cause of appearance of monsters, as the mechanical pressure on the delicate parts of the developed embryo inevitably leads to their deformation. During this, Ozeretskovskii referred to cases of development in double-yolk eggs of doubled embryos which — as a rule — are monsters. During more or less normal development of these twins, they can unite with each other. "Some years before" Ozeretskovskii wrote "we saw here, in Petersburg, doubled chickens, hatched from one egg, provided with all organs and united at the backs; when one of them stood on the legs, the other lied on it on the back with legs upwards in the most unnatural position. It is clear that,

1. N. Ozeretskovskii. De ovo perforata. There also, 12.1801, pp. 364-368.

619

only the narrowness of the shell was the cause that the twin chickens, which were pressed to each other, united by the backs, similar to the united apples, which, beginning from the moment of flowering, closely adjoined each other".

Both mentioned articles of Ozeretskovskii witness that the Russian academician considered the deformity a result of the caused changes of normal development by external influences, i.e. explained their appearance epigenetically (134).

(39) K. Fr. Kielmeyer (1765-1844), is a famous German naturalist, held in great respect by the contemporaries although he hardly left published works. The most famous work of Kielmeyer was his speech "About the relation of organic powers between each other" (1793) . Kielmeyer particularly suggested the idea of powers, inherent within the living beings — irritability, sensibility and reproduction. Their combination in the form of ascending and descending rows corresponds to the stage of the individual development as well as the stage of development of all the organic world, in which, according to Kielmeyer, "the plan of nature" is found. By comparison of the stages of development with these rows, in which adult forms may exist, Kielmeyer made a conclusion, stated by him in a conversation with Gete (1797), that the higher organisms pass many stages in the process of embryonic development, in which they become lower. Shelling attached a very great importance to the ideas of Kielmeyer considering, that they usher in a new epoch in science. In fact, he found later on that before Kielmeyer a similar idea was stated by I. G. Gerder (17441863), who was a publicist, poet and philosopher. The works of Gerder, in particular, had a relation to the question discussed — "The ideas of the philosophy of the humanity history", were highly evaluated by Gete. They were popular in Russia as well and had a known effect on Karamzin, Shevryev and Maksimovich (143) .

(40) Prince A. P. Baryatinskii a personality of the Southern Secret Society and active propagandist became, towards the end of 1825, the chief of Kilchinskaya board

(in Tul'chin the staff of the 2nd army was present, in which Pestel and some other members of Southern Secret Society served) (148) .

620

(41) Efrem Osipovich Mukhin (1766-1850) studied at

the Kharkovsky College and Elisavetgradskaya Hospital School, and then at Moscow University. He was a junior assistant at the department of pathology and therapy at Moscow Medical School, and later on a professor at the university. He wrote a great number of manual books and special works (162) .

(42) Vilglin Michailovich Rikhter (1767-1822) was born in Moscow, finished Moscow University and published a doctor's dissertation in Erlangen. From 1790 he was a professor of obstetrics at Moscow University. Rikhter is the author of project "Practical obstetrical institute" and many manual books (162) .

(43) Ivan Fedorovich Wenssowitsch (1769-1811) studied at the Kharkovsky college and Moscow University secondary school, from where he joined the university, where he successively joined the faculties of philosophy, law and medicine. He finished the university and became a candidate of medicine. In 1803, he defended a doctor's dissertation in Moscow. From 1805 he was a professor of anatomy, physiology and forensic medicine. He published "journal medico-physical He died from tuberculosis at the age of 42 (163) .

(44) Yakov Kuzmich Kaidanov (1779-1885), from Kiev Ecclesiastical Academy, studied in the Petersburg medicosurgical school. After finishing there, he was sent to Vienna to study veterinary medicine. After his return back, he became a junior assistant at the Medico-surgical Academy. From 1809, he became a