Talk:The cell in development and inheritance (1900) 9

From Embryology


" It is certain that the germ is not merely a body in which life Is dormant or potential, but that it is itself simply a detached portion of the substance of a preexisting living body.' 1

Huxley. 1

" Inheritance must be looked at as merely a form of growth." Darwin. 5

" Ich mochte daher wohl den Versuch wagen, durch eine Darstellung des Beobachtetei Sie zu einer tiefern Einsicht in die Zeugungs- und Entwickelungsgeschichte der organischen Korpcr zu fuhren und zu zeigen, wie dieselben weder vorgebildet sind, noch auch, wie mu sich gewohnlich denkt, aus ungeformter Masse in einem bestimmten Momente plotzlkh ausschiessen." Von Baejl*

Every discussion of inheritance and development must take as its point of departure the fact that the germ is a single cell similar in its essential nature to any one of the tissue-cells of which the body is composed. That a cell can carry with it the sum total of the heritage of the species, that it can in the course of a few days or weeks give rise to a mollusk or a man, is the greatest marvel of biological science. In attempting to analyze the problems that it involves, we must from the outset hold fast to the fact, on which Huxley insisted, that the wonderful formative energy of the germ is not impressed upon it from without, but is inherent in the egg as a heritage from the parental life of which it was originally a part. The development of the embryo is nothing new. It involves no breach of continuity, and is but a continuation of the vital processes going on in the parental body. What gives development its marvellous character is the rapidity with which it proceeds and the diversity of the results attained in a span so brief.

But when we have grasped this cardinal fact, we have but focussed our instruments for a study of the real problem. How do the adult characteristics lie latent in the germ-cell ; and how do they become patent as development proceeds ? This is the final question that looms in the background of every investigation of the cell. In approaching it we may well make a frank confession of ignorance ; for in spite of all that the microscope has revealed, we have not yet penetrated the mystery, and inheritance and development still remain in their fun 1 Evolution, Science and Culture, p. 291.

2 Variation of Animals and Plants* II., p. 398. 8 Entwick. der Thierc, II., 1837, P- &



damental aspects as great a riddle as they were to the Greeks. What we have gained is a tolerably precise acquaintance with the external aspects of development. The gross errors of the early preformationists have been dispelled. 1 We know that the germ-cell contains no predelineated embryo ; that development is manifested, on the one hand, by the cleavage of the egg, on the other hand, by a process of differentiation, through which the products of cleavage gradually assume diverse forms and functions, and so accomplish a physiological division of labour. We can clearly recognize the fact that these processes fall in the same category as those that take place in the tissuecells ; for the cleavage of the ovum is a form of mitotic cell-division, while, as many eminent naturalists have perceived, differentiation is nearly related to growth and has its root in the phenomena of nutrition and metabolism. The real problem of development is the orderly sequence and correlation of these phenontetia toward a typical result. We cannot escape the conclusion that this is the outcome of the organization of the germ-cells ; but the nature of that which, for lack of a better term, we call " organization/' is and doubtless long will remain almost wholly in the dark.

In the following discussion, which is necessarily compressed within narrow limits, we shall disregard the earlier baseless speculations, such as those of the seventeenth and eighteenth centuries, which attempted a merely formal solution of the problem, confining ourselves to more recent discussions that have grown directly out of modern research. An introduction to the general subject may be given by a preliminary examination of two central hypotheses about which most recent discussions have revolved. These are, first, the theory of Germinal Localisation 2 of Wilhelm His C74), and, second, the Idioplasm Hypothesis of Nageli ('84). The relation between these two conceptions, close as it is, is not at first sight very apparent ; and for the purpose of a preliminary sketch they may best be considered separately.

A. The Theory of Germinal Localization

Although the naive early theory of preformation and evolution was long since abandoned, yet we find an after-image of it in the theory of germinal localization which in one form or another has been advocated by some of the foremost students of development. It is maintained that, although the embryo is not preformed in the germ, it must nevertheless be predetermined in the sense that the egg contains

1 Cf. Introduction, p. 8.

3 I venture to suggest this term as an English equivalent for the awkward expression " Organbildende Keimbezirke " of His.


definite areas or definite substances predestined for the formation of corresponding parts of the embryonic body. The first clear statement of this conception is found in the interesting and suggestive work of Wilhelm His ('74) entitled Unsere Korperform. Considering the development of the chick, he says : " It is clear, on the one hand, that every point in the embryonic region of the blastoderm must represent a later organ or part of an organ, and, on the other hand, that every organ developed from the blastoderm has its preformed germ (vorgebildete Anlage) in a definitely located region of the flat germdisc. . . . The material of the germ is already present in the flat germ-disc, but is not yet morphologically marked off and hence not directly recognizable. But by following the development backwards we may determine the location of every such germ, even at a period when the morphological differentiation is incomplete or before it occurs ; logically, indeed, we must extend this process back to the fertilized or even the unfertilized egg. According to this principle, the germ-disc contains the organ-germs spread out in a flat plate, and, conversely, every point of the germ-disc reappears in a later organ ; I call this the principle of organ- forming germ-regions." 1 His thus conceived the embryo, not as preformed, but as having all of its parts prelocalized in the egg-protoplasm (cytoplasm).

A great impulse to this conception was given during the following decade by discoveries relating, on the one hand, to protoplasmic structure, on the other hand, to the promorphological relations of the ovum. Ray Lankester writes, in 1877: "Though the substance of a cell 2 may appear homogeneous under the most powerful microscope, it is quite possible, indeed certain, that it may contain, already formed and individualized, various kinds of physiological molecules. The visible process of segregation is only the sequel of a differentiation already established, and not visible." 8 The egg-cytoplasm has a definite molecular organization directly handed down from the parent; cleavage sunders the various " physiological molecules " and isolates them in particular cells. Whitman expresses a similar thought in the following year : " While we cannot say that the embryo is predelineated, we can say that it is predetermined. The ' histogenetic sundering ' of embryonic elements begins with the cleavage, and every step in the process bears a definite and invariable relation to antecedent and subsequent steps. ... It is, therefore, not surprising to find certain important histological differentiations and fundamental structural relations anticipated in the early phases of cleavage, and foreshadowed even before cleavage begins." 4 It was, however, Flem 1 /. c. % p. 19.

2 It is clear from the context that by " substance " lankester had in mind the cytoplasm, though this is not specifically stated. 3 '77, p. 14. * '78, p. 49.


ming who gave the first specific statement of the matter from the cytological point of view : " But if the substance of the egg-cell has a definite structure (Bau), and if this structure and the nature of the network varies in different regions of the cell-body, we may seek in it a basis for the predetermination of development wherein one egg differs from another, and it will be possible to look for it with the microscope. How far this search can be carried no one can say, but its ultimate aim is nothing less than a true morphology of inheritance l In the following year Van Beneden pointed out how nearly this conception approaches to a theory of preformation : " If this were the case (i.e. if the egg-axis coincided with the principal axis of the adult body), the old theory of evolution would not be as baseless as we think to-day. The fact that in the ascidians, and probably in other bilateral animals, the median plane of the body of the future animal is marked out from the beginning of cleavage, fully justifies the hypothesis that the materials destined to form the right side of the body are situated in one of the lateral hemispheres of the egg, while the left hemisphere gives rise to all of the organs of the left half." 2 The hypothesis thus suggested seemed, for a time, to be placed on a secure basis of fact through a remarkable experiment subsequently performed by Roux ('88) on the frog's egg. On killing one of the blastomeres of the two-cell stage by means of a heated needle the uninjured half developed in some cases into a well-formed half-larva (Fig. 182), representing approximately the right or left half of the body, containing one medulUry fold, one auditory pit, etc. 8 Analogous, though less complete, results were obtained by operating with the four-cell stage. Roux was thus led to the declaration (made with certain subsequent reservations) that " the development of the froggastrula and of the embryo formed from it is from the second cleavage onward a mosaic-work, consisting of at least four vertical independently developing pieces." 4 This conclusion seemed to form a very strong support to His's theory of germinal localization, though, as will appear beyond, Roux transferred this theory to the nucleus, and thus developed it in a very different direction from Lankester or Van Beneden. His's theory also received very strong apparent support through investigations on cell-lineage by Whitman, Rabl, and

1 Zellsuhstanz, '82, p. 70 : the italics are in the original.

2 '^ P- 571.

8 The accuracy of this result was disputed by Oscar Hertwig ('93, 1), who found that the

uninjured blastomere gave rise to a defective larva, in which certain parts were missing, but not to a true half-body. I^ater observers, especially Schultze, Kndrcs, and Morgan, have, however, shown that both Hertwig and Roux were right, proving that the uninjured blastomere may give rise to a true half-larva, to a larva with irregular defects, or to a whole larva of half-size, according to circumstances (p. 422). 4 /.r., p. 30.




many later observers, which have shown that in the cleavage of annelids, mollusks, platodes, tunicates, and many other animals, every cell has a definite origin and fate, and plays a definite part in the building of the body. 1

Pig. 1B1. — Half-embryos of the frog (in transverse section) arising from a blastomere o two-cell stage after killing the other blastomere. [Roux.]

A. Hall-blastula (dead blastomere on the left). B. Later siage. C. Half-tadpole with one medullary fold and one mesoblast plate ; regeneration of the missing (right) half in process.

or. archentcric cavity; ex. cleavage-cavity; ch. notochord; m.f. medullary fold; nij. mesoblast-plate.

In an able series of later works Whitman has followed out the suggestion made in his paper of 1878, cited above, pointing out how essential a part is played in development by the cytoplasm and insisting that cytoplasmic preorganization must be regarded as a leading factor in the ontogeny. Whitman's interesting and suggestive views are expressed with great caution and with a full recognition of the " Cf. p. 378


difficulty and complexity of the problem. From his latest essay, indeed ('94), it is not easy to gather his precise position regarding the theory of cytoplasmic localization. Through all his writings, nevertheless, runs the leading idea that the germ is definitely organized before development begins, and that cleavage only reveals an organization that exists from the beginning. " That organization precedes cell-formation and regulates it, rather than the reverse, is a conclusion that forces itself upon us from many sides." l " The organism exists before cleavage sets in, and persists throughout every stage of cell-multiplication." 2

All of these views, excepting those of Roux, lean more or less distinctly toward the conclusion that the cytoplasm of the egg-cell is from the first mapped out, as it were, into regions which correspond with the parts of the future embryonic body. The cleavage of the ovum does not create these regions, but only reveals them to view by marking off their boundaries. Their topographical arrangement in the egg does not necessarily coincide with that of the adult parts, but only involves the latter as a necessary consequence — somewhat as a picture in the kaleidoscope gives rise to a succeeding picture composed of the same parts in a different arrangement. The germinal localization may, however, in a greater or less degree, foreshadow the arrangement of adult parts — for instance, in the egg of the tunicate or cephalopod, where the bilateral symmetry and anteroposterior differentiation of the adult is foreshadowed not only in the cleavage stages, but even in the unsegmented egg.

By another set of writers, such as Roux, De Vries, Hertwig, and Weismann, germinal localization is primarily sought not in the cytoplasm, but in the nucleus ; but these views can be best considered after a review of the idioplasm hypothesis, to which we now proceed.

B. The Idioplasm Theory

We owe to Nageli the first systematic attempt to discuss heredity regarded as inherent in a definite physical basis; 3 but it is hardly necessary to point out his great debt to earlier writers, foremost among them Darwin, Herbert Spencer, and Hackel. The essence of Nageli's hypothesis was the assumption that inheritance is effected by the transmission not of a cell, considered as a whole, but of a particular substance, the idioplastn, contained within a cell, and forming the physical basis of heredity. The idioplasm is to be sharply distinguished from the other constituents of the cell, which play no direct part in inheritance and form a "nutritive plasma" or tropho 1 '93, p. 115. 3 /,c, p. 112. 8 Theorie der Abstammungslehre, 1884.



plasm. Hereditary traits are the outcome of a definite molecular organization of the idioplasm. The hen's egg differs from the frog's because it contains a different idioplasm. The species is as completely contained in the one as in the other, and the hen's egg differs from a frog's egg as widely as a hen from a frog.

The idioplasm was conceived as an extremely complex substance, consisting of elementary complexes of molecules known as micella. These are variously grouped to form units of higher orders, which, as development proceeds, determine the development of the adult cells, tissues, and organs. The specific peculiarities of the idioplasm are therefore due to the arrangement of the micellae ; and this, in its turn, is owing to dynamic properties of the micellae themselves. During development the idioplasm undergoes a progressive transformation of its substance, not through any material change, but through dynamic alterations of the conditions of tension and movement of the micellae. These changes in the idioplasm cause reactions on the part of surrounding structures leading to definite chemical and plastic changes, i.e. to differentiation and development.

Nageli made no attempt to locate the idioplasm precisely or to identify it with any of the known morphological constituents of the cell. It was somewhat vaguely conceived as a network extending through both nucleus and cytoplasm, and from cell to cell throughout the entire organism. Almost immediately after the publication of his theory, however, several of the foremost leaders of biological investigation were led to locate the idioplasm in the nucleus, and concluded that it is to be identified with chromatin. The grounds for this conclusion, which have already been stated in Chapter VII., may be here again briefly reviewed. The beautiful experiments of Nussbaum, Gruber, and Verworn proved that the regeneration of differentiated cytoplasmic structures in the Protozoa can only take place when nuclear matter is present (cf. p. 342). The study of fertilization by Hertwig, Strasburger, and Van Beneden proved that in the sexual reproduction of both plants and animals the nucleus of the germ is equally derived from both sexes, while the cytoplasm is derived almost entirely from the female. The two germ-nuclei, which by their union give rise to that of the germ, were shown by Van Beneden to be of exactly the same morphological nature, since each gives rise to chromosomes of the same number, form, and size. Van Beneden and Boveri proved (p. 182) that the paternal and maternal nuclear substances are equally distributed to each of the first two cells, and the more recent work of Hacker, Riickert, Herla, and Zoja establishes a strong probability that this equal distribution continues in the later divisions. Roux pointed out the telling fact that the entire complicated mechanism of mitosis seems designed to affect


the most accurate division of the entire nuclear substance in all of its parts, while fission of the cytoplasmic cell-body is in the main a mass-division, and not a meristic division of the individual parts. Again, the complicated processes of maturation show the significant fact that while the greatest pains is taken to prepare the germ-nuclei for their coming union, by rendering them exactly equivalent, the cytoplasm becomes widely different in the two germ-cells and is devoted to entirely different functions.

It was in the main these considerations that led Hertwig, Strasburger, Kolliker, and Weismann independently and almost simultaneously to the conclusion that the mule us contains the physical basis of inhetitance, and that chromatin^ its essential constituent, is the idioplasm postulated in NagclVs theory. This conclusion is now widely accepted and rests upon a basis so firm that it must be regarded as a working hypothesis of high value. To accept it is, however, to reject the theory of germinal localization in so far as it assumes a prelocalization of the egg-cytoplasm as a fundamental character of the egg. For if the specific character of the organism be determined by an idioplasm contained in the chromatin, then every characteristic of the cytoplasm must in the long run be determined from the same source. A striking illustration of this point is given by the phenomena of colour-inheritance in plant-hybrids, as De Vries has pointed out. Pigment is developed in the embryonic cytoplasm, which is derived from the mother-cell ; yet in hybrids it may be inherited from the male through the nucleus of the germ-cell. The specific form of cytoplasmic metabolism by which the pigment is formed must therefore be determined by the paternal chromatin in the germ-nucleus, and not by a predetermination of the egg-cytoplasm.

C. Union of the Two Theories

We have now to consider the attempts that have been made to transfer the localization-theory from the cytoplasm to the nucleus, and thus to bring it into harmony with the theory of nuclear idioplasm. These attempts are especially associated with the names of Roux, De Vries, Weismann, and Hertwig ; but all of them may be traced back to Darwin's celebrated hypothesis of pangenesis as a prototype. This hypothesis is so well known as to require but a brief review. Its fundamental postulate assumes that the germ-cells contain innumerable ultra-microscopic organized bodies or gennnules y each of which is the germ of a cell and determines the development of a similar cell during the ontogeny. The germ-cell is, therefore, in Darwin's words, a microcosm formed of a host of inconceivably minute self-propagating organisms, every one of which predetermines


the formation of one of the adult cells. De Vries ('89) brought this conception into relation with the theory of nuclear idioplasm by assuming that the gemmules of Darwin, which he called pangens, are contained in the nucleus, migrating thence into the cytoplasm step by step during ontogeny, and thus determining the successive stages of development. The hypothesis is further modified by the assumption that the pangefis are not cell-germs, as Darwin assumed, but ultimate protoplasmic units of which cells are built, and which are the bearers of particular hereditary qualities. The same view was afterward accepted by Hertwig and Weismann. 2

The theory of germinal localization is thus transferred from the cytoplasm to the nucleus. It is not denied that the egg-cytoplasm may be more or less distinctly differentiated into regions that have a constant relation to the parts of the embryo. This differentiation is, however, conceived, not as a primordial characteristic of the egg, but as one secondarily determined through the influence of the nucleus. Both De Vries and Weismann assume, in fact, that the entire cytoplasm is a product of the nucleus, being composed of pangens that migrate out from the latter, and by their active growth and multiplication build up the cytoplasmic substance. 8

D. The Roux-Weismann Theory of Development

We now proceed to an examination of two sharply opposing hypotheses of development based on the theory of nuclear idioplasm. One of these originated with Roux ('83) and has been elaborated especially by Weismann. The other was clearly outlined by De Vries ('89), and has been developed in various directions by Oscar Hertwig, Driesch, and other writers. In discussing them, it should be borne in mind that, although both have been especially developed by the advocates of the pangen-hypothesis, neither necessarily involves that hypothesis in its strict form, i.e. the postulate of discrete self-propagating units in the idioplasm. This hypothesis may therefore be laid

1 Cf. p. 290.

2 The neo-pangenesis of De Vries differs from Darwin's hypothesis in one very important respect. Darwin assumed that the gemmules arose in the body, being thrown off as germs by the individual tissue-cells, transported to the germ-cells, and there accumulated as in a reservoir; and he thus endeavoured to explain the transmission of acquired characters. De Vries, on the other hand, denies such a transportal from cell to cell, maintaining that the pangens arise or preexist in the germ-cell, and those of the tissue-cells are derived from this source by cell-division.

8 This conception obviously harmonizes with the role of the nucleus in the synthetic process. In accepting the view that the nuclear control of the cell is effected by an emanation of specific substances from the nucleus, \vc need not, however, necessarily adopt the pangen-hypothesis.


aside as an open question, 1 and will be considered only in so far as it is necessary to a presentation of the views of individual writers.

The Roux-Weismann hypothesis has already been touched on at page 245. Roux conceived the idioplasm {i.e. the chromatin) not as a single chemical compound or a homogeneous mass of molecules, but as a highly complex mixture of different substances, representing different qualities, and having their seat in the individual chromatingranules. In mitosis these become arranged in a linear series to form the spireme-thread, and hence may be precisely divided by the splitting of the thread. Roux assumes, as a fundamental postulate, that division of the granules may be either quantitative or qualitative. In the first mode the group of qualities represented in the mothergranule is first doubled and then split into equivalent daughter-groups, the daughter-cells therefore receiving the same qualities and remaining of the same nature. In "qualitative division," on the other hand, the mother-group of qualities is split into dissimilar groups, which, passing into the respective daughter-nuclei, lead to a corresponding differentiation in the daughter-cells. By qualitative divisions, occurring in a fixed and predetermined order, the idioplasm is thus split up during ontogeny into its constituent qualities, which are, as it were, sifted apart and distributed to the various nuclei of the embryo. Every cell-nucleus, therefore, receives a specific form of chromatin which determines the nature of the cell at a given period and its later history. Every cell is thus endowed with a power of selfdcter?nination, which lies in the specific structure of its nucleus, and its course of development is only in a minor degree capable of modification through the relation of the cell to its fellows (" correlative differentiation ").

Roux's hypothesis, be it observed, does not commit him to the theory of pangenesis. It was reserved for Weismann to develop the hypothesis of qualitative division in terms of the pangen-hypothesis, and to elaborate it as a complete theory of development. In his first essay ('85), published before De Vries's paper, he went no farther than Roux. " I believe that we must accept the hypothesis that in indirect nuclear division, the formation of non-equivalent halves may take place quite as readily as the formation of equivalent halves, and that the equivalence or non-equivalence of the subsequently produced daughter-cells must depend upon that of the nuclei. Thus, during ontogeny a gradual transformation of the nuclear substance takes place, necessarily imposed upon it, according to certain laws, by its own nature, and such transformation is accompanied by a gradual change in the character of the cell-bodies." 2 In later writings Weismann advanced far beyond this, building up an elaborate artificial system, which appears in its final form in the remarkable

1 Cf. Chapter VI. 2 Essay IV., p. 193, 1885.


book on the germ-plasm ('92 ). Accepting De Vries's conception of the pangens, he assumes a definite grouping of these bodies in the germ-plasm or idioplasm (chromatin), somewhat as in Nagelfs conception. The pangens or biophores are conceived to be successively aggregated in larger and larger groups; namely, (1) determinants, which are still beyond the limits of microscopical vision; (2) ids, which are identified with the visible chromatin-granules ; and (3) idants, or chromosomes. The chromatin has, therefore, a highly complex fixed architecture, which is transmitted from generation to generation, and determines the development of the embryo in a definite and specific manner. Mitotic division is conceived as an apparatus which may distribute the elements of the chromatin to the daughter-nuclei either equally or unequally. In the former case (" homoeokinesis," integral or quantitative division), the resulting nuclei remain precisely equivalent. In the second case (" heterokinesis" qualitative ox differential division), the daughter-cells receive different groups of chromatinelements, and hence become differently modified. During ontogeny, through successive qualitative divisions, the elements of the idioplasm or germ-plasm (chromatin) are gradually sifted apart, and distributed in a definite and predetermined manner to the various parts of the body. " Ontogeny depends on a gradual process of disintegration of the id of germ-plasm, which splits into smaller and smaller groups of determinants in the development of each individual. . . . Finally, if we neglect possible complications, only one kind of determinant remains in each cell, viz. that which has to control that particular cell or group of cells. ... In this cell it breaks up into its constituent biophores, and gives the cell its inherited specific character." 1 Development is, therefore, essentially evolutionary and not epigenetic ; 2 its point of departure is a substance in which all of the adult characters are represented by preformed, prearranged germs ; its course is the result of a predetermined harmony in the succession of the qualitative divisions by which the hereditary substance is progressively disintegrated. In order to account for heredity through successive generations, Weismann is obliged to assume that, by means of quantitative or integral division, a certain part of the original germ-plasm is carried on unchanged, and is finally delivered, with its original architecture unaltered, to the germ-nuclei. The power of regeneration is explained, in like manner, as the result of a transmission of unmodified or slightly modified germ-plasm to those parts capable of regeneration.

1 Germ-plasm y pp. 76, 77. 2 /.<-., p. 15.


E. Critique of the Roux-Weismann Theory

It is impossible not to admire the thoroughness, candour, and logical skill with which Weismann has developed his theory, or to deny that, in its 6nal form, it does afford up to a certain point a formal solution of the problems with which it deals. Its fundamental weakness is its ^«<«;-metaphysical character, which, indeed, almost places it outside


Fig. 183. — Hair and who

A. Normal sixtecn-cell stage, showing th B. Half sixteen-ccll stage developed from 01 by shaking (Driesch). C. Half blaslula r IX Half-sized six!een-cell Mage of Toiopnti iown>. This embryo, developed from

like at

cleavage in the eggs of sea-urchins.

four micromeres above (from Driesch, after Selenka).

blaslomere of Ihe two-cell stage after killing the oilier

<ulling. [he dead blaslomere at the right (I)riesch). Its, viewed from Ihe micromere-potc (the eighl lower n isolated blaslomere of the two-cell stage, segmented

the sphere of legitimate scientific hypothesis. Save in the maturation of the germ-cells ("reducing divisions"), none of the visible phenomena of cell-division give even a remote suggestion of qualitative division. All the facts of ordinary mitosis, on the contrary, indicate that the division of the chromatin is carried out with the most exact equality,



The hypothesis mainly rests upon a quite different order of phenomena, namely, on facts indicating that isolated blastomeres, or other cells, have a certain power of self-determination, or " self-differentiation" (Roux), peculiar to themselves, and which is assumed to be primarily due to the specific quality of the nuclei. This assumption, which may or may not be true, 1 is itself based upon the further assumption of qualitative nuclear division of which we actually know nothing whatever. The fundamental hypothesis is thus of purely a priori character; and every fact opposed to it has been met by subsidi

Fig. 184. — Normal and dwarf gastrulas of Amphioxus.

A. Normal gastrula. B. Half-sized dwarf, from an isolated blastomere of the two-cell stage. C. Quarter-sized dwarf, from an isolated blastomere of the four-cell stage.

ary hypotheses, which, like their principal, relate to matters beyond the reach of observation.

Such an hypothesis cannot be actually overturned by a direct appeal to fact. We can, however, make an indirect appeal, the results of which show that the hypothesis of qualitative division is not only so improbable as to lose all semblance of reality, but is in fact quite superfluous. It is rather remarkable that Roux himself led the way in this direction. In the course of his observations on the development of a half-embryo from one of the blastomeres of the two-cell stage of the frog's egg f he determined the significant fact that the half-embryo in the end restores more or less completely

1 Cf.p. 426.



the missing half by a peculiar process, related to regeneration, which Roux designated as post-generation. Later studies showed that an isolated blastomere is able to give rise to a complete embryo in many other animals, sometimes developing in its earlier stages as though

Fig. 185,.- Dwarf and

ouble embryos of

A. Isolated blaslomere of [he two-cell si

ige segmenting like

B. Twin gaBtrulas from a single egg. O'Do

by shaking, of the blastomeres of the two-eel

stage. D.EJ-'. D

forms as the last

still forming part of a complete embryo ("partial development"), but in other cases developing directly into a complete dwarf embryo, as if it were an egg of diminished size. In 1891 Driesch was able to follow out the development of isolated blastomeres of sea-urchin


eggs separated by shaking to pieces the two-cell and four-cell stages. Blastomeres thus isolated segment as if still forming part of an entire larva, and give rise to a half- (or quarter-) blastula (Fig. 183). The opening soon closes, however, to form a small complete blastula, and the resulting gastrula and Pluteus larva is a perfectly formed dwarf of only half (or quarter) the normal size. Incompletely separated blastomeres give rise to double embryos like the Siamese twins. Shortly afterward the writer obtained similar results in the case of Amphioxus, but here the isolated bias tome re behaves from the beginning like a complete ovum of half the usual size, and gives rise to a complete blastula, gastrula, and larva. Complete embryos have also been obtained from a single blastomere in the teleost Fundulus (Morgan, '95, 2), in Triton (Herlitzka, '95), and in a number of hydromedusae (Zoja, '95, Bunting, '99); and nearly complete embryos in the tunicates Ascidiella (Chabry, '87), Phallusia (Driesch, '94), and Molgula (Crampton, '98). 1 Perhaps the most striking of these cases is that of the hydroid Clytia y in which Zoja was able to obtain perfect embryos, not only from the blastomeres of the twoceil and four-cell stages, but from eight-cell and even from sixteenceli stages, the dwarfs in the last case being but one-sixteenth the normal size.

These experiments render highly improbable the hypothesis of qualitative division in its strict form, for they demonstrate that the earlier cleavages, at least, do not in these cases sunder fundamentally different materials, either nuclear or cytoplasmic, but only split the egg up into a number of parts, each of which is capable of producing an entire body of diminished size, and hence must contain all of the material essential to complete development. Both Roux and Weismann endeavour to meet this adverse evidence with the assumption of a " reserve idioplasm," containing all of the elements of the germplasm which is in these cases distributed equally to all the cells in addition to the specific chromatin conveyed to them by qualitative division. This subsidiary hypothesis renders the principal one {i.e. that of qualitative division) superfluous, and brings us back to the same problems that arise when the assumption of qualitative division is discarded.

The theory of qualitative nuclear division has been practically disproved in another way by Driesch, through the pressure-experiments already mentioned at page 375. Following the earlier experiments of Pfliiger ('84) and Roux ('85) on the frog's cgg f Driesch subjected segmenting eggs of the sea-urchin to pressure, and thus obtained flat plates of cells in which the arrangement of the nuclei differed totally

1 The " partial " development in the earlier stages of some of these forms is considered at page 419.



from the normal (Fig. 186); yet such eggs when released from pressure continue to segment, without rearrangement of the nuclei, and give rise to perfectly normal larvae. I have repeated these experiments not only with sea-urchin eggs, but also with those of an annelid {Nereis), which yield a very convincing result, since in this case the histological differentiation of the cells appears very early. In the normal development of this animal the archenteron arises from four large cells or macromeres (entomeres), which remain after the successive formation of three quartets of micromeres (ectomeres) and the parent-cell of the mesoblast. After the primary differentiation of the germ-layers the four entomeres do not divide again until a very late period (free-swimming trochophore), and their substance always retains a characteristic appearance, differing from that of the other

Pig. 186. — Modification of cleavage in sea-urchin eggs by pressure.

A. Normal eight-cell stage of Toxopruustes. B. Eight-cell stage of Echinus segmenting under pressure. Both forms produce normal Flutei.

blastomeres in its pale non-granular character and in the presence of large oil-drops. If unsegmented eggs be subjected to pressure, as in Driesch's echinoderm experiments, they segment in a flat plate, all of the cleavages being vertical. In this way are formed eight-celled plates in which all of the cells contain oil-drops (Fig. 187, D). If they are now released from the pressure, each of the cells divides in a plane approximately horizontal, a smaller granular micromere being formed above, leaving below a larger clear macromere in which the oil-drops remain. The sixteen-cell stage, therefore, consists of eight deutoplasm-laden macromeres and eight protoplasmic micromeres (instead of four macromeres and twelve micromeres, as in the usual development). These embryos developed into free-swimming trochophores containing eight instead of four macromeres, which have the typical clear protoplasm containing oil-drops. In this case there can



be no doubt whatever that four of the entoblastic nuclei were normally destined for the first quartet of micromeres (Fig. 187, B), from which arise the apical ganglia and the prototroch. Under the conditions of the experiment, however, they have given rise to the nuclei of cells which differ in no wise from the other entoderm-cells. Even

Fig. 187. — Modifications of cleavage by pressure in Nereis.

A. B. Normal four- and eight-cell stages. C. Normal trochophore larva resulting, with four entoderm-cells. D. Eight-cell stage arising from an egg flattened by pressure ; such eggs give rise to trochophores with eight instead of four entoderm-cells. Numerals designate the successive cleavages.

in a highly differentiated type of cleavage, therefore, the nuclei of the segmenting egg are not specifically different, as the Roux-Weismann hypothesis demands, but contain the same materials even in the cells that undergo the most diverse subsequent fate. But there is, furthermore, very strong reason for believing that this may be true in later


stages as well, as Kolliker insisted in opposition to Weismann as early as 1886, and as has been urged by many subsequent writers. The strongest evidence in this direction is afforded by the facts of regeneration ; and many cases are known — for instance, among the hydroids and the plants — in which even a small fragment of the body is able to reproduce the whole. It is true that the power of regeneration is always limited to a greater or less extent according to the species. But there is no evidence whatever that such limitation arises through specification of the nuclei by qualitative division, and, as will appear beyond, its explanation is probably to be sought in a very different direction.

F. On the Nature and Causes of Differentiation

We have now cleared the ground for a restatement of the problem of development and an examination of the views opposed to the Roux-Weismann theory. After discarding the hypothesis of qualitative division the problem confronts us in the following form. If chromatin be the idioplasm in which inheres the sum total of hereditary forces, and if it be equally distributed at every cell-division, how can its mode of action so vary in different cells as to cause diversity of structure, i.e. differentiation ? It is perfectly certain that differentiation is an actual progressive transformation of the egg-substance involving both physical and chemical changes, occurring in a definite order, and showing a definite distribution in the regions of the egg. These changes are sooner or later accompanied by the cleavage of the egg into cells whose boundaries may sharply mark the areas of differentiation. What gives these cells their specific character? Why, in the four-cell stage of an annelid egg, should the four cells contribute equally to the formation of the alimentary canal and the cephalic nervous system, while only one of them (the lefthand posterior) gives rise to the nervous system of the trunk-region and to the muscles, connective tissues, and the germ-cells? (Figs. 171, 188, £.) There cannot be a fixed relation between the various regions of the egg which these blastomeres represent and the adult parts arising from them ; for in some eggs these relations may be artificially changed. A portion of the egg which under normal conditions would give rise to only a fragment of the body will, if split off from the rest, give rise to an entire body of diminished size. What then determines the history of such a portion? What influence moulds it now into an entire body, now into a part of a body ?

De Vries, in his remarkable essay on Intracellular Pangenesis ('89), endeavoured to cut this Gordian knot by assuming that the character of each cell is determined by pangens that migrate from



the nucleus into the cytoplasm, and, there becoming active, set up specific changes and determine the character of the cell, this way or that, according to their nature. But what influence guides the migrations of the pangens, and so correlates the operations of development? Both Driesch and Oscar Hertwig have attempted to

Fig. i88. - Diagrams il

lustratingthe value of the quanclE in a polyclade {I*ptoplana\ . n [amel

[[branch (Unto), and a gs

slrronod {Crepidula). A. Lrfhflama, showing mesoblast-formatioii

in the second qu;ir!ct. //.

lom«5oh].is[ ifmm tjuiidrjiH

1 11). (.'. Uhio, eclomesoblasl formed only from j".

Inallthi' figures Ihesucc

essIyb quarleis are numbered with Arabic figures ; ecloblasl unshaded.

mesoblest dolled, enloblasr

vertically lined.

answer this question, though the first-named author does not commit himself to the pangen-hypothesis. These writers have maintained that the particular mode of development in a given region or blastomere of the egg is a result of its relation to the remainder of the mass, i.e. a product of what may be called the intra-em'bryonic environ


ment. Hertwig insisted that the organism develops as a whole as the result of a physiological interaction of equivalent blastomeres, the transformation of each being due not to an inherent specific power of self-differentiation, as Roux's mosaic-theory assumed, but to the action upon it of the whole system of which it is a part. "According to my conception," said Hertwig, "each of the first two blastomeres contains the formative and differentiating forces not simply for the production of a half-body, but for the entire organism ; the left blastomere develops into the left half of the body only because it is placed in relation to a right blastomere." l Again, in a later paper : " The egg is a specifically organized elementary organism that develops epigenetically by breaking up into cells and their subsequent differentiation. Since every elementary part (i.e. cell) arises through the division of the germ, or fertilized Qgg f it contains also the germ of the whole, but during the process of development it becomes ever more precisely differentiated and determined by the formation of cytoplasmic products according to its position with reference to the entire organism (blastula, gastrula, etc.)." 2

An essentially similar view was advocated by the writer ('93, '94) nearly at the same time, and the same general conception was expressed with great clearness and precision by Driesch shortly after Hertwig: "The fragments (i.e. cells) produced by cleavage are completely equivalent or indifferent." "The blastomeres of the seaurchin are to be regarded as forming a uniform material, and they may be thrown about, like balls in a pile, without in the least degree impairing thereby the normal power of development." 3 " The relative position of a blastomere in the whole determines in general what develops from it ; if its position be changed, it gives rise to something different ; in other words, its prospective value is a f miction of its position. " 4

In this last aphorism the whole problem of development is brought to a focus. It is clearly not a solution of the problem, but only a highly suggestive restatement of it ; for everything turns upon how the relation of the part to the whole is conceived. Very little consideration is required to show that this relation cannot be a merely geometrical or rudely mechanical one, for in the eggs of different

1 '92, 1, p. 481.

2 '93» P- 793- It should be pointed out that Roux himself in several papers expressly recognizes the fact that development cannot be regarded as a pure mosaic-work, and that besides the power of self-differentiation postulated by his hypothesis we must assume a " correlative differentiation " or differentiating interaction of parts in the embryo. Cf. Roux, '92, '93, 1.

8 Studien IV., p. 25.

  • Studien IV., p. 39. Cf. His, " Es muss die Wachsthumserregbarkeit des Eies eine

Function des Raumes sein." ('74, p. 153.)


animals blastomeres may almost exactly correspond in origin and relative position, yet differ widely in their relation to the resulting embryo. Thus we find that the cleavage of polyclades, annelids, and gasteropods (Fig. 188) shows a really wonderful agreement in form, yet the individual cells differ markedly in prospective value. In all of these forms three quartets of micromeres are successively formed according to exactly the same remarkable law of the alternation of the spirals ; l and, in all, the posterior cell of a fourth quartet lies at the hinder end of the embryo in precisely the same geometrical relation to the remainder of the embryo ; yet in the gasteropods and annelids this cell gives rise to the mesoblast-bands and their products, in the polyclade to a part of the archenteron, while important differences also exist in the value of the other quartets. The relation of the part to the whole is therefore of a highly subtle character, the prospective value of a blastomere depending not merely upon its geometrical position, but upon its relation to the whole complex inherited organization of which it forms a part. The apparently simple conclusion stated in Driesch's clever aphorism thus leads to further problems of the highest complexity. It should be here pointed out that Driesch does not accept Hertwig's theory of the interaction of blastomeres as such, but, like Whitman, Morgan, and others, has brought forward effective arguments against that too simple and mechanical conception. That theory is, in fact, merely Schwann's cell-composite theory of the organism applied to the developing embryo, and the general arguments against that theory find some of their strongest support in the facts of growth and development. 2 This has been forcibly urged by Whitman ('93), who almost simultaneously with the statements of Driesch and Hertwig, cited above, expressed the conviction that the morphogenic process cannot be conceived as merely the sum total or resultant of the individual cell-activities, but operates as a unit without respect to cell-boundaries, precisely as De Bary concludes in the case of growing plant-tissues (p. 393), and the nature of that process is due to the organization of the egg as a whole.

While recognizing fully the great value of the results attained during the past few years in the field of experimental and speculative embryology, we are constrained to admit that as far as the essence of the problem is concerned we have not gone very far beyond the conclusions stated above ; for beyond the fact that the inherited organization is involved in that of the germ-cells we remain quite ignorant of its essential nature. This has been recognized by no one more clearly than by Driesch himself, to whose critical researches we owe so much in this field. At the climax of a recent elaborate analysis, the high interest of which is somewhat obscured by

1 Cf. p. 368. * Cf. pp. 38S-394.


its too abstruse form, Driesch can only reiterate his former aphorism, 1 finally taking refuge in an avowed theory of vitalism which assumes the localization of morphogenic phenomena to be determined by "a wholly unknown principle of correlation/' 2 and forms a problem sui generis? This conclusion recognizes the fact that the fundamental problem of development remains wholly unsolved, thus confirming from a new point of view a conclusion which it is only fair to point out has been reached by many others.

But while the fundamental nature of the morphogenic process thus remains unknown, we have learned some very interesting facts regarding the conditions under which it takes place, and which show that Driesch's aphorism loses its meaning unless carefully qualified. The experiments referred to at pages 353, 410, show that up to a certain stage of development the blastomeres of the early echinoderm, Amp/iioxus or medusa-embryo, are " totipotent " (Roux), or "equipotential" (Driesch), i.e. capable of producing any or all parts of the body. Even in these cases, however, we cannot accept the early conclusion of Pfliiger ('83), applied by him to the frog's egg, and afterward accepted by Hertwig, that the material of the egg f or of the blastomeres into which it splits up, is absolutely "isotropic," i.e. consists of quite uniform indifferent material, devoid of preestablished axes. Whitman and Morgan, and Driesch himself, showed that this cannot be the case in the echinoderm Qgg\ for the ovum possesses a polarity predetermined before cleavage begins, as proved by the fact that at the fourth cleavage a group of small cells or micromeres always arises at a certain point, which may be precisely located before cleavage by reference to the eccentricity of the first cleavage-nucleus, 4 and which, as Morgan showed, 6 is indicated before the third, and sometimes before the second cleavage, by a migration of pigment away from the micromere-pole. These observers are thus led to the assumption of a primary polarity of the egg-protoplasm, to which Driesch, in the course of further analysis of the phenomena, is compelled to add the assumption of a secondary polarity at right angles to the first. 6 These polarities, inherent not only in the entire egg, but also in each of the blastomeres into which it divides, form the primary conditions under which the bilaterally symmetrical organism develops by epigenesis. To this extent, therefore, the material of the blastomeres, though " totipotent,' ' shows a certain predetermination with respect to the adult body.

1 '99, pp. 86-87.

2 This phrase is cited by Driesch from an earlier work ('92, p. 596) as giving a correct though " unanalytical " statement of his view. It may be questioned whether many readers will regard as an improvement the " analytical " form it assumes in his last work.

  • I.e., p. 90. 4 Cf. Fig. 103. 6 '94, p. 142.

6 See Driesch, '93, pp. 229, 241 ; '96, and '99, p. 44. 2 £


We now proceed to the consideration of experiments which show that in some animal eggs such predetermination may go much farther, so that the development does, in fact, show many of the features of a mosaic-work, as maintained by Roux. The best-determined of these cases is that of the ctenophore-egg, as shown by the work of Chun,

ihore Brroi. [DmEscH and MORGAN.] n isolated blaslomere. B. Resuming larva, with (our i

ows of pl.iles and two gastric pouches. E. '. trie pouches, from a nucleated fragment of a

Driesch, and Morgan ('95), and Fischel ('98). These observers have demonstrated that isolated blastomeres of the two-, four-, or eight-cell stage undergo a cleavage which, through the earliest stages, is exactly like that which it would have undergone if forming part of a com



plete embryo, and gives rise to a defective larva, having only four, two, or one row of swimming-plates (Fig. 189); and Fischer s observations give strong reason to believe that each of the eight micromeres of the sixteen-cell stage is definitely specified for the formation of one of the rows of plates. In like manner Crampton ('96) found that in case of the marine gasteropod Ilyanassa isolated blastomeres of twocell or four-cell stages segmented exactly as if forming part of an entire embryo, and gave rise to fragments of a larva, not to complete dwarfs, as in the echinoderm (Fig. 190). Further, in embryos from which the " yolk-lobe w (a region of that macromere from which the primary mesoblast normally arises) had been removed, no mesoblastbands were formed. Most interesting of all, Driesch and Morgan discovered that if a part of the cytoplasm of an unscgmented ctenophore-egg were removed, the remainder gave rise to an incomplete larva, showing definite defects (Fig. 189, E, F).

In none of these cases is the embryo able to complete itself, though it should be remarked that neither in the ctenophore nor in the snail is the partial embryo identical with a fragment of a whole embryo, since the micromeres finally enclose the macromeres, leaving no surface of fracture. This extreme is, however, connected by a series of forms with such cases as those of Amphioxus or the medusa, where the fragment develops nearly or quite as if it were a whole. In the tunicates the researches of Chabry ('87), Driesch ('94), and Crampton C97) show that an isolated blastomere of the two-cell stage undergoes a typical half-cleavage (Crampton), but finally gives rise to a nearly perfect tadpole larva lacking only one of the asymmetrically placed sense-organs (Driesch). Next in the series may be placed the frog, where, as Roux, Endres, and Walter have shown, a blastomere of the two-cell stage may give rise to a typical half-morula, half-gastrula, and half-embryo 1 (Fig. 182), yet finally produces a perfect larva. A further stage is given by the echinoderm-egg, which, as Driesch showed, undergoes a half-cleavage and produces a haif-blastula, which, however, closes to form a whole before the gastrula-stage (Fig. 183). Perfectly formed though dwarf larvae result. Finally, we reach Amphioxus and the hydromasae in which a perfect " whole development " usually takes place from the beginning, though it is a very interesting fact that the isolated blastomeres of Amphioxus sometimes show, in the early stages of cleavage, peculiarities of development that recall their behaviour when forming part of an entire embryo. 2

We see throughout this series an effort, as it were, on the part of the isolated blastomere to assume the mode of development characteristic of a complete egg, but one that is striving against conditions that

1 This is not invariably the case, as described beyond.

2 Cf. Wilson, '93, pp. 590, 608.



tend to confine its operations to the rdle it would have played if still forming part of an entire developing egg. In Amphioxus or Ctytia this tendency is successful almost from the beginning. In other forms the limiting conditions are only overcome at a later period, while in the ctenophore or snail they seem to afford an insurmount

A. Normal eight-cell stage. B. Normal sixteen sola ted hi asto mere of Ihe mo-cell stage. D. Halfr n the cleavage of an isolated hlastomere of the four-cell stage jelow a one-fourth sixteen-cell stage.

c. C. Half eight-cell stage, from stace succeeding. E. Two stains ahove a one-fourth eight-cell stage.

able barrier to complete development. What determines the limitations of development in these various cases ? They cannot be due to nuclear specification ; for in the ctenophore the fragment of an Hi/segmented egg, containing the normal egg-nucleus, gives rise to a defective larva; and my experiments on Nereis show that even in a highly



determinate cleavage, essentially like that of the snail, the nuclei may be shifted about by pressure without altering the end-result. Neither can they lie in the form of the dividing mass as some authors have assumed ; for in Crampton's experiments the half or quarter blastomere does not retain the form of a half or quarter sphere, but rounds

Pig. 191. — Double embryos of frog developed from eggs in' JO. Schui.tzeJ

A. Twins with heads turned in opposite directions. B. Twi united by their ventral sides. D. Double-headed tadpole.

rted when in the Iwo-cell stage, < united back to back. C. Twin*

off to a spheroid like the egg. But if the limiting conditions lie neither in the nucleus nor in the form of the mass, we must seek them in the cytoplasm ; and if we find here factors by which the tendency of the part to develop into a whole may be, as it were, hemmed in, we shall reach a proximate explanation of the mosaic-like character of cleavage shown in the forms under consideration, and the mosaic


theory of cytoplasmic localization will find a substantial if somewhat restricted basis.

That we are here approaching the true explanation is indicated by certain very remarkable and interesting experiments on the frog's egg t which prove that each of the first two blastomeres may give rise either to a half-embryo or to a whole embryo of half size, according to circumstances, and which indicate, furthermore, that these circumstances lie in a measure in the arrangement of the cytoplasmic materials. This most important result, which we owe especially to Morgan, 1 was reached in the following manner. Born had shown, in 1885, that if frogs' eggs be fastened in an abnormal position, — e.g. upside down, or on the side, — a rearrangement of the egg-material takes place, the heavier deutoplasm sinking toward the lower side, while the nucleus and protoplasm rise. A new axis is this established in the egg-, which has the same relation to the body-axes as in the ordinary development (though the pigment retains its original arrangement). This proves that in eggs of this character (telolecithal) the distribution of deutoplasm, or conversely of protoplasm, is one of the primary formative conditions of the cytoplasm ; and the significant fact is that by artificially changing this distribution the axis of the embryo is shifted. Oscar Schultze ('94) discovered that if the egg be turned upside down when in the two-cell stage, a whole embryo (or half of a double embryo) may arise from each blastomere instead of a half-embryo as in the normal development, and that the axes of these embryos show no constant relation to one another (Fig. 191). Morgan ('95, 3) added the important discovery that either a half-embryo or a whole half-sized dwarf might be formed, according to the position of the blastomere. If, after destruction of one blastomere, the other be allowed to remain in its normal position, a half -embryo always results, 2 precisely as described by Roux. If, on the other hand, the blastomere be inverted, it may give rise either to a half-embryo 3 or to a whole dwarf. 4 Morgan therefore concluded that the production of whole embryos by the inverted blastomeres was, in part at least, due to a rearrangement or rotation of the egg-materials under the influence of gravity, the blastomere thus returning, as it were, to a state of equilibrium like that of an entire ovum.

This beautiful experiment gives most conclusive evidence that each of the two blastomeres contains all the materials, nuclear and cytoplasmic, necessary for the formation of a whole body ; and that these materials may be used to build a whole body or half-body, according to the grouping that they assume. After the first cleavage takes

1 Anat. Anz., X. 19, 1895. 8 Three cases.

a Eleven cases observed. * Nine cases observed.


place, each blastomere is set, as it were, for a half-development, but not so firmly that a rearrangement is excluded.

I have reached a nearly related result in the case of both Amp hioxus and the echinoderms. In Amphioxus the isolated blastomere usually segments like an entire ovum of diminished size. This is, however, not invariable, for a certain number of such blastomeres show a more or less marked tendency to divide as if still forming part of an entire embryo. The sea-urchin Toxopnetistes reverses this rule, for the isolated blastomere of the two-cell stage usually shows a perfectly typical half-cleavage, as described by Driesch, but in rare cases it may segment like an entire ovum of half-size(Fig. 183, Z?)and give rise to an entire blastula. We may interpret this to mean that in Amphioxus the differentiation of the cytoplasmic substance is at first very slight, or readily alterable, so that the isolated blastomere, as a rule, reverts at once to the condition of the entire ovum. In the seaurchin, the initial differentiations are more extensive or more firmly established, so that only exceptionally can they be altered. In the snail and ctenophore we have the opposite extreme to Amphioxus, the cytoplasmic conditions having been so firmly established that they cannot be readjusted, and the development must, from the outset, proceed within the limits thus set up.

Through this conclusion we reconcile, as I believe, the theories of cytoplasmic localization and mosaic development with the hypothesis of cytoplasmic totipotence. Primarily the egg-cytoplasm is totipotent in the sense that its various regions stand in no fixed relation with the parts to which they respectively give rise, and the substance of each of the blastomeres into which it splits up contains all of the materials necessary to the formation of a complete body. Secondarily, however, development may assume more or less of a mosaic-like character through differentiations of the cytoplasmic substance involving local chemical and physical changes, deposits of metaplasmic material, and doubtless many other unknown subtler processes. Both the extent and the rate of such differentiations seem to vary in different cases; and here probably lies the explanation of the fact that the isolated blastomeres of different eggs vary so widely in their mode of development. When the initial differentiation is of small extent or is of such a kind as to be readily modified, cleavage is indeterminate in character and may easily be remodelled (as in Amphioxus). When they are more extensive or more rigid, cleavage assumes a mosaic-like or determinate character, 1 and qualitative division, in a certain sense, becomes a fact. Conklin's ('99) interesting observations on the highly determinate cleavage of gasteropods {Crepiduld)

1 The convenient terms indeterminate and determinate cleavage were suggested by Conklin ('98).



show that here the substance of the attraction-spheres is unequally distributed, in a quite definite way, among the cleavage-ceils, each sphere of a daughter-cell being carried over bodily into one of the granddaughter-cells (Fig. 192). We have here a substantial basis for the conclusion that in cleavage of this type qualitative division of the cytoplasm may occur.

It is important not to lose sight of the fact that development and differentiation do not in any proper sense first begin with the cleavage of the ovum, but long before this, during its ovarian history. 1 The primary differentiations thus established in the cytoplasm form the immediate conditions to which the later development must conform; and the difference between Amphioxus on the one hand, and the


Fig. 191. — Two successive stages in the third cleavage of the egg of CrtpiduL upper pole. [CoNKLIN.]

In both figures the old spheres (dotted) lie at the upper pole of the embryo, i cleavage they pass into the four respective cells of the first quartet of micromeri somes are seen in the neu spheres.

ind at the third

snail or ctenophore on the other, simply means, I think, that the initial differentiation is less extensive or less firmly established in the one than in the other.

The origin of the cytoplasmic differentiations existing at the beginning of cleavage has already been considered (p. 386). If the conclusions there reached be placed beside the above, we reach the following conception. The primary determining cause of development lies in the nucleus, which operates by setting up a continuous series of specific metabolic changes in the cytoplasm. This process begins during ovarian growth, establishing the external form of the egg, its primary polarity, and the distribution of substances within it. The cytoplasmic differentiations thus set up form as it were a frame1 See Wilson ('96), Driesch ('98, 1).


work within which the subsequent operations take place in a course which is more or less firmly fixed in different cases. If the cytoplasmic conditions be artificially altered by isolation or other disturbance of the blastomeres, a readjustment may take place and development may be correspondingly altered. Whether such a readjustment is possible depends on secondary factors — the extent of the primary differentiations, the physical consistency of the eggsubstance, the susceptibility of the protoplasm to injury, and doubtless a multitude of others. The same doubtless applies to the later stages of development ; and we must here seek for some of the factors by which the power of regeneration in the adult is determined and limited. It is, however, not improbable, as pointed out below, that in the later stages differentiation may occur in the nuclear as well as in the cytoplasmic substance.

G. The Nucleus in Later Development

The foregoing conception, as far as it goes, gives at least an intelligible view of the more general features of early development and in a measure harmonizes the apparently conflicting results of experiment on various forms. But there are a very large number of facts relating especially to the later stages of differentiation, which it seems to leave unexplained* and which indicate that the nucleus as well as the cytoplasm may undergo progressive changes of its substance. It has been assumed by most critics of the Roux- Weismann theory that all of the nuclei of the body contain the same idioplasm, and that each therefore, in Hertwig's words, contains the germ of the whole. It is, however, doubtful whether this assumption is well founded. The power of a single cell to produce the entire body is in general limited to the earliest stages of cleavage, rapidly diminishes, and as a rule soon disappears entirely. When once the germ-layers have been definitely separated, they lose entirely the power to regenerate one another save in a few exceptional cases. In asexual reproduction, in the regeneration of lost parts, in the formation of morbid growths, each tissue is in general able to reproduce only a tissue of its own or a nearly related kind. Transplanted or transposed groups of cells (grafts and the like) retain more or less. completely their autonomy and vary only within certain well-defined limits, despite their change of environment. All of these statements are, it is true, subject to exception ; yet the facts afford an overwhelming demonstration that differentiated cells possess a specific character, that their power of development and adaptability to changed conditions becomes in a greater or less degree limited with the progress of development. As indicated above, this progressive specification of the tissue-cells


is no doubt due in part to differentiation of the cytoplasm. There is, however, reason to suspect that, beyond this, differentiation may sooner or later involve a specification of the nuclear substance. When we reflect on the general role of the nucleus in metabolism and its significance as the especial seat of the formative power, we may well hesitate to deny that this part of Roux's conception may be better founded than his critics have admitted. Nageli insisted that the idioplasm must undergo a progressive transformation during development, and many subsequent writers, including such acute thinkers as Boveri and Nussbaum, and many pathologists, have recognized the necessity for such an assumption. Boveri's remarkable observations on the nuclei of the primordial germ-cells in Ascaris demonstrate the truth of this view in a particular case ; for here all oft/ie somatic nuclei lose a portion of their chromatin, and only the progenitors of the germ-neclei retain the entire ancestral heritage. Boveri himself has in a measure pointed out the significance of his discovery, insisting that the specific development of the tissue-cells is conditioned by specific changes in the chromatin that they receive, 1 though he is careful not to commit himself to any definite theory. It hardly seems possible to doubt that in Ascaris the limitation of the somatic cells in respect to the power of development arises through a loss of particular portions of the chromatin. One cannot avoid the thought that further and more specific limitations in the various forms of somatic cells may arise through an analogous process, and that we have here a key to the origin of nuclear specification without recourse to the theory of qualitative division. We do not need to assume that the unused chromatin is cast out bodily ; for it may degenerate and dissolve, or may be transformed into linin-substance or into nucleoli.

This suggestion is made only as a tentative hypothesis, but the phenomena of mitosis seem well worthy of consideration from this point of view. Its application to the facts of development becomes clearer when we consider the nature of the nuclear "control" of the cell, i.e. the action of the nucleus upon the cytoplasm. Strasburger, following in a measure the lines laid down by Nageli, regards the action as essentially dynamic, i.e. as a propagation of molecular movements from nucleus to cytoplasm in a manner which might be compared to the transmission of a nervous impulse. When, however, we consider the role of the nucleus in synthetic metabolism, and the relation between this process and that of morphological synthesis, we must regard the question in another light ; and opinion has of late strongly tended to the conclusion that nuclear "control" can only be explained as the result of active exchanges of material between nucleus and cytoplasm. De Vries, followed by Hertwig,

1 '9>» p. 433


assumes a migration of pangens from nucleus to cytoplasm, the character of the cell being determined by the nature of the migrating pangens, and these being, as it were, selected by circumstances (position of the cell, etc.). But, as already pointed out, the pangenhypothesis should be held quite distinct from the purely physiological aspect of the question, and may be temporarily set aside; for specific nuclear substances may pass from the nucleus into the cytoplasm in an unorganized form. Sachs, followed by Loeb, has advanced the hypothesis that the development of particular organs is determined by specific " formative substances " which incite corresponding forms of metabolic activity, growth, and differentiation. It is but a step from this to the very interesting suggestion of Driesch that the nucleus is a storehouse of ferments which pass out into the cytoplasm and there set up specific activities. Under the influence of these ferments the cytoplasmic organization is determined at every step of the development, and new conditions are established for the ensuing change. This view is put forward only tentatively as a " fiction " or working hypothesis ; but it is certainly full of suggestion. Could we establish the fact that the number of ferments or formative substances in the nucleus diminishes with the progress of differentiation, we should have a comparatively simple and intelligible explanation of the specification of nuclei and the limitation of development. The power of regeneration might then be conceived, somewhat as in the Roux-Weismann theory, as due to a retention of idioplasm or germ-plasm — i.e. chromatin — in a less highly modified condition, and the differences between the various tissues in this regard, or between related organisms, would find a natural explanation.

Development may thus be conceived as a progressive transformation of the egg-substance primarily incited by the nucleus, first manifesting itself by specific changes in the cytoplasm, but sooner or later involving in some measure the nuclear substance itself. This process, which one is tempted to compare to a complicated and progressive form of crystallization, begins with the youngest ovarian egg and proceeds continuously until the cycle of individual life has run its course. Cell-division is an accompaniment but not a direct cause of differentiation. The cell is no more than a particular area of the germinal substance comprising a certain quantity of cytoplasm and a mass of idioplasm in its nucleus. Its character is primarily a manifestation of the general formative energy acting at a particular point under given conditions. When once such a circumscribed area has been established, it may, however, emancipate itself in a greater or less degree from the remainder of the mass, and acquire a specific character so fixed as to be incapable of further change save within the limits imposed by its acquired character.


H. The External Conditions of Development

We have thus far considered only the internal conditions of development which are progressively created by the germ-cell itself. We must now briefly glance at the external conditions afforded by the environment of the embryo. That development is conditioned by the external environment is obvious. But we have only recently

to realize how intimate the relation is; and it has been especially the

service of Loeb, Herbst, and Driesch to show how essential a part is played by the environment in the development of specific organic forms. The limits of this work will not admit of any adequate review of the vast array of known facts in this field, for which the reader is referred to the works especially of Herbst. I shall only consider one or two cases which may serve to bring out the general principle that they involve. Every living organism at every stage of its existence reacts to its environment by physiological and morphological changes. The developing embryo, like the adult, is a moving equilibrium — a product of the response of the inherited organization to the external stimuli working upon it. If these stimuli be altered, development is altered. This is beautifully shown by the experiments of Herbst and others on the development of sea-urchins. Pouchet and Chabry showed that if the embryos of these animals be made to develop in sea-water containing no lime-salts, the larva fails to develop not only its calcareous skeleton, but also its ciliated arms, and a larva thus results that resembles in some particulars an entirely different specific form ; namely, the Tornaria larva of Balanoglossus. This result is not due simply to the lack of necessary material : for Herbst showed that the same result is attained if a slight excess of potassium chloride be added to sea-water containing the normal amount of lime (Fig. 193). In the latter case the specific metabolism of the protoplasm is altered by a particular chemical stimulus, and a new form results.

Fig. 193-


  • slight ;


The changes thus caused by slight chemical alterations in the water may be still more profound. Herbst ('92) observed, for example, that when the water contains a very small percentage of lithium chloride, the blastula of sea-urchins fails to invaginate to form a typical gastrula, but evaginates to form an hour-glass-shaped

A. Polyp (CtriaMfiHi), prodi B. Hydroid ( TWn/ar/j), general water. C. D. Similar generalion of heai

larva, one half of which represents the archenteron, the other half the ectoblast. Moreover, a much larger number of the blastula-cells undergo the differentiation into entoblast than in the normal development, the ectoblast sometimes becoming greatly reduced and occasionally disappearing altogether, so that the entire blastula is


differentiated into cells having the histological character of the normal entoblast ! One of the most fundamental of embryonic differentiations is thus shown to be intimately conditioned by the chemical environment.

The observations of botanists on the production of roots and other structures as the result of local stimuli are familiar to all. Loeb's interesting experiments on hydroids give a similar result ('91). It has long been known that Tubularia, like many other hydroids, has the power to regenerate its " head " — i.e. hypostome, mouth, and tentacles — after decapitation. Loeb proved that in this case the power to form a new head is conditioned by the environment. For if a Tnbnlaria stem be cut off at both ends and inserted in the sand upside down, i.e. with the oral end buried, a new head is regenerated at the free (formerly aboral) end. Moreover, if such a piece be suspended in the water by its middle point, a new head is produced at each end (Fig. 194); while if both ends be buried in the sand, neither end regenerates. This proves in the clearest manner that in this case the power to form a definite complicated structure is called forth by the stimulus of the external environment.

These cases must suffice for our purpose. They prove incontestably that normal development is in a greater or less degree the response of the developing organism to normal conditions ; and they show that we cannot hope to solve the problems of development without reckoning with these conditions. But neither can we regard specific forms of development as directly caused by the external conditions ; for the egg of a fish and that of a polyp develop, side by side, in the same drop of water, under identical conditions, each into its predestined form. Every step of development is a physiological reaction, involving a long and complex chain of cause and effect between the stimulus and the response. The character of the response is determined, not by the stimulus, but by the inherited organization. While, therefore, the study of the external conditions is essential to the analysis of embryological phenomena, it serves only to reveal the mode of action of the germ and gives but a dim insight into its ultimate nature.

I. Development, Inheritance, and Metabolism

In bringing the foregoing discussion into more direct relation with the general theory of cell-action, we may recall that the cell-nucleus appears to us in two apparently different roles. On the one hand, it is a primary factor in morphological synthesis and hence in inheritance, on the other hand an organ of metabolism especially concerned with the constructive process. These two functions we may with


Claude Bernard regard as but different phases of one process. The building of a definite cell-product, such as a muscle-fibre, a nerveprocess, a cilium, a pigment-granule, a zymogen-granule, is in the last analysis the result of a specific form of metabolic activity, as we may conclude from the fact that such products have not only a definite physical and morphological character, but also a definite chemical character. In its physiological aspect, therefore, inheritance is the recurrence, in successive generations, of like forms of metabolism ; and this is effected through the transmission from generation to generation of a specific substance or idioplasm which we have seen reason to identify with chromatin. The validity of this conception is not affected by the form in which we conceive the morphological nature of the idioplasm — whether as simply a mixture of chemical substances, as a microcosm of invisible germs or pangens, as assumed by De Vries, Weismann, and Hertwig, as a storehouse of specific ferments as Driesch suggests, or as a complex molecular substance grouped in micellae as in Nageli's hypothesis. It is true, as Verworn insists, that the cytoplasm is essential to inheritance ; for without a specifically organized cytoplasm the nucleus is unable to set up specific forms of synthesis. This objection, which has already been considered from different points of view, by both De Vries and Driesch, disappears as soon as we regard the egg-cytoplasm as itself a product of the nuclear activity ; and it is just here that the general rdle of the nucleus in metabolism is of such vital importance to the theory of inheritance. If the nucleus be the formative centre of the cell, if nutritive substances be elaborated by or under the influence of the nucleus while they are built into the living fabric, then the specific character of the cytoplasm is determined by that of the nucleus, and the contradiction vanishes. In accepting this view we admit that the cytoplasm of the egg is, in a measure, the substratum of inheritance, but it is so only by virtue of its relation to the nucleus, which is, so to speak, the ultimate court of appeal. The nucleus cannot operate without a cytoplasmic field in which its peculiar powers may come into play ; but this field is created and moulded by itself.

J. Preformation and Epigenesis. The Unknown Factor in


We have now arrived at the farthest outposts of cell-research, and here we find ourselves confronted with the same unsolved problems before which the investigators of evolution have made a halt. For we must now inquire what is the guiding principle of embryological development that correlates its complex phenomena and directs them


to a definite end. However we conceive the special mechanism of development, we cannot escape the conclusion that the power behind it is involved in the structure of the germ-plasm inherited from foregoing generations. What is the nature of this structure and how has it been acquired ? To the first of these questions we have as yet no certain answer. The second question is merely the general problem of evolution stated from the standpoint of the cell-theory. The first question raises once more the old puzzle of preformation or epigenesis. The pangen-hypothesis of De Vries and Weismann recognizes the fact that development is epigenetic in its external features ; but like Darwin's hypothesis of pangenesis, it is at bottom a theory of preformation, and Weismann expresses the conviction that an epigenetic development is an impossibility. 1 He thus explicitly adopts the view, long since suggested by Huxley, that "the process which in its superficial aspect is epigenesis appears in essence to be evolution in the modified sense adopted in Bonnet's later writings ; and development is merely the expansion of a potential organism or 'original preformation ' according to fixed laws." 2 Hertwig ('92, 2), while accepting the pangen-hypothesis, endeavours to take a middle ground between preformation and epigenesis, by assuming that the pangens (idioblasts) represent only cell-characters, the traits of the multicellular body arising epigenetically by permutations and combinations of these characters. This conception certainly tends to simplify our ideas of development in its outward features, but it does not explain why cells of different characters should be combined in a definite manner, and hence does not reach the ultimate problem of inheritance.

What lies beyond our reach at present, as Driesch has very ably urged, is to explain the orderly rhythm of development — the coordinating power that guides development to its predestined end. We are logically compelled to refer this power to the inherent organization of the germ, but we neither know nor can we even conceive what that organization is. The theory of Roux and Weismann demands for the orderly distribution of the elements of the germ-plasm a prearranged system of forces of absolutely inconceivable complexity. Hertwig's and De Vries's theory, though apparently simpler, makes no less a demand ; for how are we to conceive the power which guides the countless hosts of migrating pangens throughout all the long and complex events of development? The same difficulty confronts us under any theory we can frame. If with Herbert Spencer we assume the germ-plasm to be an aggregation of like units, molecular or supra-molecular, endowed with predetermined polarities which lead to their grouping in specific forms,

1 Germ-plasm, p. 14. 2 Evolution, Science, and Culture* p. 296.


we but throw the problem one stage farther back, and, as Weismann himself has pointed out, 1 substitute for one difficulty another of exactly the same kind.

The truth is that an explanation of development is at present beyond our reach. The controversy between preformation and epigenesis has now arrived at a stage where it has little meaning apart from the general problem of physical causality. What we know is that a specific kind of living substance, derived from the parent, tends to run through a specific cycle of changes during which it transforms itself into a body like that of which it formed a part ; and we are able to study with greater or less precision the mechanism by which that transformation is effected and the conditions under which it takes place. But despite all our theories we no more know how the organization of the germ-cell involves the properties of the adult body than we know how the properties of hydrogen and oxygen involve those of water. So long as the chemist and physicist are unable to solve so simple a problem of physical causality as this, the embryologist may well be content to reserve his judgment on a problem a hundred-fold more complex.

The second question, regarding the historical origin of the idioplasm, brings us to the side of the evolutionists. The idioplasm of every species has been derived, as we must believe, by the modification of a preexisting idioplasm through variation, and the survival of the fittest. Whether these variations first arise in the idioplasm of the germ-cells, as Weismann maintains, or whether they may arise in the body-cells and then be reflected back upon the idioplasm, is a question to which the study of the cell has thus far given no certain answer. Whatever position we take on this question, the same difficulty is encountered ; namely, the origin of that coordinated fitness, that power of active adjustment between internal and external relations, which, as so many eminent biological thinkers have insisted, overshadows every manifestation of life. The nature and origin of this power is the fundamental problem of biology. When, after removing the lens of the eye in the larval salamander, we see it restored in perfect and typical form by regeneration from the posterior layer of the iris, 2 we behold an adaptive response to changed conditions of which the organism can have had no antecedent experience either ontogenetic or phylogenetic, and one of so marvellous a character that we are made to realize, as by a flash of light, how far we still are from a solution of this problem. It may be true, as Schwann himself urged, that the adaptive power of living beings differs in degree only, not in kind, from that of unor 1 Germinal Selection, January, 1896, p. 284. 8 See Wolff, '95, and Miiller, '96.



ganized bodies. It is true that we may trace in organic nature long and finely graduated series leading upward from the lower to the higher forms, and we must believe that the wonderful adaptive manifestations of the more complex forms have been derived from simpler conditions through the progressive operation of natural causes. But when all these admissions are made, and when the conserving action of natural selection is in the fullest degree recognized, we cannot close our eyes to two facts : first, that we are utterly ignorant of the manner in which the idioplasm of the germ-cell can so respond to the influence of the environment as to call forth an adaptive variation ; and second, that the study of the cell has on the whole seemed to widen rather than to narrow the enormous gap that separates even the lowest forms of life from the inorganic world.

I am well aware that to many such a conclusion may appear reactionary or even to involve a renunciation of what has been regarded as the ultimate aim of biology. In reply to such a criticism I can only express my conviction that the magnitude of the problem of development, whether ontogenetic or phylogenetic, has been underestimated ; and that the progress of science is retarded rather than advanced by a premature attack upon its ultimate problems. Yet the splendid achievements of cell-research in the past twenty years stand as the promise of its possibilities for the future, and we need set no limit to its advance. To Schleiden and Schwann the present standpoint of the cell-theory might well have seemed unattainable We cannot foretell its future triumphs, nor can we doubt that the way has already been opened to better understanding of inheritance and development.


Barfurth, D. — Regeneration und Involution: Merkel u. Bonnet, Ergeb. y I .-VI 1 1.

1891-99. Boveri, Th. — Ein geschlechtlich erzeugter Organismus ohne mutterliche Eigen schaften: Sit z.- Iter. d. Ges.f. Morph. und Phys. in Munchen, V. 1889. Sec

also Arch. f. Entw. 1895. Brooks, W. K. — The Law of Heredity. Baltimore, 1883. Id. — The Foundations of Zoology. New York, 1899.

Davenport, C. B. — Experimental Morphology: I., II. New York, 1897, 1899. Driesch, H. — Analvtische Theorie der organischen Entwicklung. Leipzig* 1894. Id. — Die Localisation morphogenetischer Vorgange: Arch. Entw., VII. 1. 1899. Id. — Resultate und Probleme der Entwickelungs-physiologie der Tiere : Merkel u.

Bonnet, Frgeb., VIII., 1898. (Full literature.) Herbst, C. — Uber die Bedeutung der Reizphysiologie fur die kausale Auffassung

von Vorgangen in der tierischen Ontogenese: Biol. Centralb., XIV., XV.

1894-95. Eertwig, 0. — Altere und neuere Entwicklungs-theorien. Berlin, 1892.


Hertwig, 0. — Urmund und Spina Bifida: Arch. mik. Anat., XXXIX. 1892. Id. — Uber den Werth der Ersten Furchungszellen fiir die Organbildung des Embryo: Arch. mik. Anat., XLII. 1893. Id. — Zeit und Streitfragen der Biologic I. Berlin, 1894. II. Jena, 1897. Id. — Die Zelle und die Gewebe, II. Jena, 1898. His, W. — Unsere Korperform und das physiologische Problem ihrer Entstehung.

Leipzig* 1874. Loeb» J. — Untersuchungen zur physiologischen Morphologie : I. Heteromorphosis.

IViirzburg, 1891. II. Organbildung und Wachsthum. WUrzburg, 1892. Id. — Some Facts and Principles of Physiological Morphology: Wood's Holl Biol.

Lectures. 1893. Morgan, T. H. — Experimental Studies of the Regeneration of Phanaria Maculata :

Arch. Entw., VII. 2, 3. 1898. Id. — The Development of the Frog's Egg. New York, 1897. Nageli, C. — Mechahisch-physiologische Theorie der Abstammungslehre. Afiin chen u. Leipzig, 1884. Rous, W. — Uber die Bedeutung der Kernteilungsfiguren. Leipzig, 1883. Id. — Ober das kunstliche Hervorbringen halber Embryonen durch Zerstorung einer

der beiden ersten Furchungskugeln, etc. : Virchovfs Archiv, 114. 1888. Id. — Fiir unsere Programme und seine Verwirklichung : Arch. Entw., V. 2. 1897.

(See also Gesammelte Abhandlungen liber Entwicklungsmechanik der Organ ismen, 1895.) Sachs, J. — Stoflf und Form der Pflanzenorgane : Ges. Abhandlungen, II. 1893. Weismann, A. — Essays upon Heredity, First Series. Oxford, 1891. Id. — Essays upon Heredity, Second Series. Oxford, 1892. Id. — Aussere Einfllisse als Entwicklungsreize. Jena, 1894. Id. — The Germ-plasm. New York* 1893.

Whitman, C. 0. — Evolution and Epigenesis : Wood's Moll Biol. Lectures. 1894. Wilson, Edm. B. — On Cleavage and Mosaic-work: Arch, fur Entwicklungsm. y

III. 1. 1896. See also Literature, VIII., p. 394.)


[Obsolete terms are enclosed in brackets. The name and date refer to the first use of the word ;

subsequent changes of meaning are indicated in the definition.]

Achro'matin (see Chromatin), the non-staining substance of the nucleus, as opposed to chromatin ; comprising the ground-substance and the linin-network. (Flemming, 1879.)

A'croaome ( axpov, apex, oxS/jo, body), the apical body situated at the anterior end of head of spermatozoon. (Lenhossek, 1897.)

[Akaryo'ta] (see Karyota), non-nucleated cells. (Flemming, 1882.)

Ale'cithal (d-priv. ; Ac'kl0o?, the yolk of an egg), having little or no yolk (applied to eggs). (Balfour, 1880.)

AUoplasma'tic (aAAo?, different). Applied to active substances formed by differentiation from the protoplasm proper, e.g. the substance of cilia, of nerve-fibrillae, and of muscle-fibrillae. Alloplasmatic organs are opposed to " protoplasmatic," which arise only by division of preexisting bodies of the same kind. (A. Meyer, 1896.)

Amito'sis (see Mitosis), direct or amitotic nuclear division; mass-division of the nuclear substance without the formation of chromosomes and amphiaster. (Flemming, 1882.)

Amphiaster (dfi<^t, on both sides ; don/p, a star), the achromatic figure formed in mitotic cell-division, consisting of two asters connected by a spindle. (Fol,

1877) Amphipy'renin (see Py renin), the substance of the nuclear membrane.

(SCHWARZ, 1887.)

Amy'loplasts (dfivXov, starch ; irAaoro?, irAao-o-eLv, form), the colourless starchforming plastids of plant-cells. (Errera, 1882.)

An'aphase (dva, back or again), the later period of mitosis during the divergence of the daughter-chromosomes. (Strasburger, 1884.)

Aniso'tropy (see Isotropy), having a predetermined axis or axes (as applied to the egg) . ( Pfl'uger, 1883.)

Antherozo'id, the same as Spermatosoid.

Anti'podal cone, the cone of astral rays opposite to the spindle-fibres. (Van Beneden, 1883.)

Archiam'phiaster (dp\t = first, + amphiaster), the amphiaster by which the first or second polar body is formed. (Whitman, 1878.)

Ar'choplasma or Archoplasm (ap\u)v, a ruler) (sometimes written archt'plasm), the substance from which the attraction-sphere, the astral rays, and the spindlefibres are developed, and of which they consist. (Boveri, 1888.)

Arrhe'noid (apprjv, male). The sperm-aster or attraction-sphere formed during the fertilization of the ovum. (Henking, 1890.)

As'ter (aoTiJp, a star). 1. The star-shaped structure surrounding the centrosome. (Fol, 1877.) [2. The star-shaped group of chromosomes during mitosis (see Karyaster). (Flemming, 1892.)]

[As'troccele] (dori;p, a star ; koIXos, hollow), a term somewhat vaguely applied to the space in which the centrosome lies. (Fol, 1891.)



As'trosphere (see Centrocphere). i. The central mass of the aster, exclusive of the rays, in which the centrosome lies. Equivalent to the -attraction-sphere" of Van Beneden. (Fou 1891 : Strasbirger. 1892.) 2. The entire aster exclusive of the centrosome. Equivalent to the - astral sphere ~ of Mark. (Boveri. 1895.)

Attraction-sphere (see Centrosphere), the central mass of the aster from which the rays proceed. Also the mass of - archoplasm." derived from the aster, by which the centrosome is surrounded in the resting cell. (Van Bexeden, 1885.)

[Au'toblast] (auroc. self), applied by Altmann to bacteria and other minute organisms, conceived as independent solitary "bioplasts." (1890.)

Axial filament, the central filament probably contractile, of the spermatozoonnagellum. (Eimer, 1874.)

Baaichro' matin (see Chromatin), the same as chromatin in the usual sense. That portion of the nuclear network stained by basic tar-colours. (Hexdexhain. 1894.)

Bi'oblast (fiios. life : /Jaooto?. a germ), a term applied by Altmann to the hypothetical ultimate vital unit (equivalent to piasome), and identified by him as the u granulum. r '

Bi'ogen (/ftb?, life ; -ycvijs, producing), equivalent to plasonu, etc ( Verworx, 1895.)

Bi'ophores (/Kbc, life ; -<t>6ptK. bearing), the ultimate supra-molecular vital units. Equivalent to the pangens of De Vries, the plasomes of Wiesner, etc (Weismaxn. 1893.)

Bi'oplasm (/ftb?, xAa?/ia). The active "living, forming germinal material,"* as opposed to 4i formed material.** Nearly equivalent to protoplasm in the wider sense. (Beale. 1870.)

Bi'oplast, equivalent to cell. (Beale, 1870.)

Bivalent, applied to chromatin-rods representing two chromosomes joined end to end. (Hacker, 1892.)

Ble pharoplast (#Ac<£apts, eye-lash or cilium). The centrosome-like bodies in plant-spermatids in connection with which the cilia of the spermatozoids are formed. (Webber, 1897.)

Cell-plate (see Mid -body), the equatorial thickening of the spindle-fibres from which the partition-wall arises during the division of plant-cells. (Strasburger, 1875.)

Cell-sap. the more liquid ground-substance of the nucleus. [Kolliker, 1865: more precisely denned by R. Hertwig, 1876.]

Central spindle, the primary spindle by which the centrosomes are connected, as opposed to the contractile mantle-fibres surrounding it. (Hermann, 1891.)

Cen'triole, a term applied by Boveri to a minute body or bodies (•' Central -korn") within the centrosome. In some cases not to be distinguished from the centrosome. (Boveri, 1895.)

Centrodes miis (jccVrpov. centre; 8e?/io?, a band), the primary connection between the centrosomes, formed by a substance from which arises the central spindle. (Heidenmain, 1894.)

Centrodeu'toplasm, the granular material of the testis-cells which may contribute to the formation of the Nebenkern or to that of the idiozome. (Erlanger, 1897.)

Centrole cithal (KcVrpov, centre ; Ac'ki0os. yolk), that type of ovum in which the deutoplasm is mainly accumulated in the centre. (Balfour, 1880.)

Cen troplasm (xcVrpov, centre ; -rrkdafjua). the protoplasm forming the attractionsphere or central region of the aster ; the substance of the centrosphere. (Erlanger, 1895.)


Cen'troaome (Kcvrpov, centre ; crco/ua, body), a body found at the centre of the aster or attraction-sphere, regarded by some observers as the active centre of celldivision and in this sense as the dynamic centre of the cell. Under its influence arise the asters and spindle (amphiaster) of the mitotic figure. (Boveri, 1888.)

Cen'troaphere, used in this work as equivalent to the " astrosphere " of Strasburger ; the central mass of the aster from which the rays proceed and within which lies the centrosome. The attraction-sphere. [Strasburger, 1892; applied by him to the " astrosphere " and centrosome taken together.]

Chloroplaa'tids (\\<M>p6s, green ; irAaoros, form), the green plastids or chlorophyllbodies of plant and animal cells. (Schimper, 1883.)

Chromatin (xp<o/ia, colour), the deeply staining substance of the nuclear network and of the chromosomes, consisting of nuclein. (Flemmixg, 1879.)

Chro'matophore (xpcS/ja, colour ; -<f>6p<y;, bearing), a general term applied to the coloured plastids of plant and animal cells, including chloroplastids and chromo plastids. (SCHAARSCHMIDT, l88o; SCHMITZ, 1882.)

Chro'matoplaam (xpwpa, colour ; irAaa/ia, anything formed or moulded), the substance of the chromoplastids and other plastids. (Strasburger, 1882.)

Chro'miole, the smallest chromatin-granules which by their aggregation form the larger chromomeres of which the chromosomes are composed. (Eisen, 1899.)

Chro'momere (xpw/ja, colour; fiipos, a part), one of the chromatin-granules of which the chromosomes are made up. Identified by Weismann as the *'id." See Chromiole. (Fol, 1891.)

Chromoplas'tidB (xpwpa, colour ; 7rAaoro5, form), the coloured plastids or pigmentbodies other than the chloroplasts, in plant-cells. (Schimper, 1883.)

Chro'moplaats, net-knots or chromatin-nucleoli; also used by some authors as equivalent to Chromoplaatid. (Eisen, 1899.)

Chromosomes (xpu/ia, colour; oxo/m, body), the deeply staining bodies into which the chromatic nuclear network resolves itself during mitotic cell-division. (Waldeyer, 1888.)

Cleavage-nucleus, the nucleus of the fertilized egg, resulting from the union of egg-nucleus and sperm-nucleus. (O. Hertwig, 1875.)

Cortical zone, the outer zone of the centrosphere. (Van Beneden, 1887.)

Cyano'philous (kvolvos, blue ; <^iA.ctv, to love), having an especial affinity for blue or green dyes. (Auerbach.)

Cy 'taster (mrros, hollow (a cell) ; acrrqp, star), the same as Aster, 1. See Karyaster. (Flemming, 1882.)

[Cy'toblast] (mrros, hollow (a cell); /JAaoros, germ). 1. The cell-nucleus. (Schleiden, 1838.) 2. One of the hypothetical ultimate vital units (bioblasts or "granula") of which the cell is built up. (Altmann, 1890.) 3. A naked cell or " protoblast." (Kolliker. )

fCytoblaate'ma] (see Cytoblast), the formative material from which cells were supposed to arise by "free cell-formation." (Schleiden, 1838.)

[Cytochyle'ma] (mrros, hollow (a cell) : xvAos juice), the ground-substance of the cytoplasm as opposed to that of the nucleus. (Strasburger, 1882.)

Cy'tode (kvtos, hollow (a cell) ; ci8o<», form), a non-nucleated cell. (Hackel, 1866.)

Cytodie'resia (kvtos, hollow (a cell) ; (Wpccris, division), the same as Mitosis. (Henneguy, 188?.)

Cytohy'aloplaama (jcvtos, hollow (a cell) ; vaAo?, glass ; 7rAao-/xa, anything formed), the substance of the cytoreticulum in which are embedded the microsomes; opposed to nucleohyaloplasma. (Strasburger, 1882.) •

Cy'tolymph (kvtos. hollow (a cell) ; lympha, clear water), the cytoplasmic groundsubstance. (Hackel, 1891.)


Cytomi'crosomes (see Microsome), microsomes of the cytoplasm ; opposed to nucleomicrosomes. (Strasburger, 1882.)

Cytomi'tome (kvtos. hollow (a cell) ; /u'ra>/ua, from furos, thread), the cytoplasmic as opposed to the nuclear thread-work. (Flemming, 1882.)

Cy'toplasm (kvtck, irXaxTyua). 1. The protoplasmic ground-substance as opposed to the granules. (Kolliker, 1863.) 2. Equivalent to protoplasm. (Kolliker. 1867.) 3. The substance of the cell-body as opposed to that of the nucleus. (Strasburger, 1882.)

Cytoretic'ulum, the same as Cytomitome. (Strasburger, 1882.)

Cy'tosome (kvtogj hollow (a cell) ; <ru>/xa, body). 1. The cell-body or cytoplasmic mass as opposed to the nucleus. (Hackel, 1891.) 2. A term used as parallel to chromosome to denote deeply staining definitely organized cytoplasmic filaments or other cytoplasmic structures composed of ** cytochromatin." ( Prenant, i 898. )

Der'matoplasm (Scp/xa, skin), the living protoplasm asserted to form a part of the cell-membrane in plants. (Wiesner, 1886.)

Der'matosomes (Sepfia, skin ; ow/ao, body), the plasomes which form the cell-membrane. (Wiesner, 1886.)

Determinant, a hypothetical unit formed as an aggregation of biophores, determining the development of a single cell or independently variable group of cells. (Weismann, 1 891.)

[Deuthy alosome] (8evr(cpos), second ; see Hyalosome), the nucleus remaining in the egg after formation of the first polar body. (Van Beneden, 1883.)

Deu'toplasm (8evr(cpos), second ; irkdo-fAa, anything formed), yolk, lifeless foodmatters deposited in the cytoplasm of the egg ; opposed to "protoplasm." (Van Beneden, 1870.)

Diakine'sis (81a, through), the segmented-spireme-stage, following the synapsis, in the primary oocyte or spermatocyte, during which the chromosomes persist for a considerable period in the form of double rods. (Hacker, 1897.)

Directive bodies, the polar bodies. (Fr. MCller, 1848.)

Directive sphere, the attraction-sphere. (Guignard, 1891.)

Dispermy, the entrance of two spermatozoa into the egg.

Dispi'reme (see Spireme), that stage of mitosis in which each daughter-nucleus has given rise to a spireme. (Flemming, 1882.)

Dy'aster (8vas. two; see Aster, 2), the double group of chromosomes during the anaphases of cell-division. (Flemming, 1882.)

Ectosphere (£ktos, outside), the outer or cortical zone of the attraction-sphere. (Ziegler, 1899.)

Egg-nucleus, the nucleus of the egg after formation of the polar bodies and before its union with the sperm-nucleus. Equivalent to the "female pronucleus'" of Van Beneden. (O. Hertwig, 1875.)

Enchyle'ma (cV, in ; xvAos, juice). 1 . The more fluid portion of protoplasm, consisting of " hyaloplasma." (Hanstein, 1880.) 2. The ground-substance (cytolymph) of cytoplasm as opposed to the reticulum. (Carnoy, 1883.)

Endoplast, the cell-nucleus. (Huxley, 1853.)

Ener'gid, the cell-nucleus together with the cytoplasm lying within its sphere of influence. (Sachs, 1892.)

Untosphere, (cVrds, inside), the inner or medullary zone of the attraction-sphere. (Ziegler, 1899.)

Equatorial plate, the group of chromosomes lying at the equator of the spindle during mitosis. (Van Beneden, 1875.)

Ergastic ( epyafo/uai, to work). Applied to relatively passive substances "formed anew through activity of the protoplasm. ,, Equivalent to metaplasmic. Cf* alloplasmatic. (A. Meyer, 1896.)


Ergastoplasm (cpya£o/iai, to work). Nearly equivalent to the " kinoplasm n of

Strasburger and the *' ergoplasm " of Davidoff. The more active protoplasmic

substance from which fibrillar formations arise. (Garnier, 1897.) Ergoplasm (cpyov, work). The active protoplasm of the egg (in tunicates), mainly

derived from the achromatic part of the germinal vesicle, and giving rise in part

or wholly to the polar spindle. Analogous to archoplasm and kinoplasm.

(Davidoff, 1889.) Erythro'philous (ipvQpos, red ; <^iyc?v, to love), having an especial affinity for red

dyes. (Auerbach.) Ga'mete (yafienj, wife ; yafierrp, husband), one of two conjugating cells. Usually

applied to the unicellular forms. Gem/mule (see Pangen), one of the ultimate supra-molecular germs of the cell

assumed by Darwin. (Darwin, 1868.) [Ge'noblasts] (yews, sex ; /ftooros, germ), a term applied by Minot to the mature

germ-cells. The female genoblast (egg or " thelyblast ") unites with the male

(spermatozoon or ** arsenoblast ") to form an hermaphrodite or indifferent cell.

(Minot, 1877.) Germinal spot, the nucleolus of the germinal vesicle. (Wagner, 1836.) Germinal vesicle, the nucleus of the egg before formation of the polar bodies.

(Purkinje, 1825.) Germ-plasm, the same as idioplasm. (Weismann.) Heterokine'sis (crcpos, different), qualitative nuclear division ; a hypothetical mode

of mitosis assumed to separate chromatins of different quality; opposed to

homookinesis or equation-division. (Weismann, 1892.) Heterole'cithal (ercpos, different; A.c'ja0O9, yolk), having unequally distributed

deutoplasm (includes telolecithal and centrolecithal) . (Mark, 1892.) Heterotyp'ical mitosis (crcpos, different ; see Mitosis), that mode of mitotic

division in which the daughter-chromosomes remain united by their ends to form

rings. (Flemming, 1887.) [Holoschi'sis] (0A09, whole ; crxt£civ, to split), direct nuclear division. Amitosis.

(Flemming, 1882.) Homole'cithal (ofxoq, the same, uniform ; Acfcttfo?, yolk), equivalent to alecithal.

Having little deutoplasm, equally distributed, or none. (Mark, 1892.) Homottkine'sis or Homasokine'sis (6/109, the same), equation-division, separating

equivalent chromatins; opposed to heterokinesis. (Weismann, 1892.) Homceotyp'ical mitosis (0/1010?, like ; see Mitosis), a form of mitosis occurring

in the secondary spermatocytes of the salamander, differing from the usual type

only in the shortness of the chromosomes and the irregular arrangement of

the daughter-chromosomes. (Flemming, 1887.) Hy'aloplasma (uoAoc, glass ; 7rAao>ui, anything formed). 1. The ground-substance

of the cell as distinguished from the granules or microsomes. [Hanstein, 1880.]

2. The achromatic substance of the nucleus in which the chromatin-particles are

embedded. (Strasburger, 1882.) 3. The ground-substance as distinguished

from the reticulum or "spongioplasm." (Leydig, 1885.) 4. The exoplasm or

peripheral protoplasmic zone in plant-cells. (Pfeffer.) Hy'alosomes (vaAos, glass ; ow/ia, body), nucleolar-like bodies but slightly stained

by either nuclear or plasma stains. (Lukjanow, 1888.) [Hy'groplasma] (vypos, wet; 7rAao>ia, something formed), the more liquid part

of protoplasm as opposed to the firmer stereoplasm. (Nageli, 1884.) Id, the hypothetical structural unit resulting from the successive aggregation of

biophores and determinants. Identified by Weismann as the chromomere, or

chromatin-granule. (W t eismann. 1891.) Idant, the hypothetical unit resulting from the successive aggregation of biophores,


determinants, and Ids. Identified by Weismann as the chromosome. (Weismakn, 1 89 1.)

Id'ioblasts (18109* one's own ; pXaaros, germ), the hypothetical ultimate units of the cell ; the same as biophores. (O. Hertwig, 1893.)

Idioplasm (18109, one's own ; irXatrfm, a thing formed), equivalent to the germplasm of Weismann. The substance, now generally identified with chromatin, which by its inherent organization involves the characteristics of the species. The physical basis of inheritance. (Nageli, 1884.)

Id'iosome (18109, one's own; oxu/ia, body), the same as idioblast or plasome. (Whitman, 1893.)

Idiozome (18109, specially formed ; £o>/ia, girdle) . The sphere, often called attraction-sphere and usually enclosing the centrosomes, found in the spermatids of animals. (Meves, 1897.)

Interfilar substance, the ground-substance of protoplasm as opposed to the threadwork. (Flemming, 1882.)

Interzonal fibres (" Filaments reunissants " of Van Beneden. " Verbindungsfasern" of Flemming and others). Those spindle-fibres that stretch between the two groups of daughter-chromosomes during the anaphase. Equivalent in some cases to the central spindle. (Mark, 1881.)

Iso'tropy (10-09, equal; tooth}, a turning), the absence of predetermined axes (as applied to the egg). (Pfluger, 1883.)

[Ka'ryaster] (tcapvov, nut, nucleus ; see Aster, 2), the star-shaped group of chromosomes in mitosis. Opposed to cytaster. (Flemming, 1882.)

Karyenchy'ma (tcdpvov, nut, nucleus; iv, in; \ v H^y juice), the "nuclear sap." (Flemming, 1882.)

Karyokine'sis {napvov, nut, nucleus; kivtjctls, change, movement), the same as mitosis. (Schleicher, 1878.)

[Karyoly'ma], the " karyolytic " (mitotic) figure. (Auerbach, 1876.)

Ka'ryolymph. The nuclear sap. (Hackel, 1891.)

[Karyo'lysis] (xapvov, nut, nucleus ; A.ixn9, dissolution), the supposed dissolution of the nucleus during cell-division. (Auerbach, 1874.)

[Karyoly'tic figure] (see Karyolysis), a term applied by Auerbach to the mitotic figure in living cells. Believed by him to result from the dissolution of the nucleus. (Auerbach, 1874.)

Karyomi'crosome (see Microsome), the same as nucleo-microsome.

Karyomi'tome (xapvov, nut, nucleus ; /x/royia, from /X1Y09, a thread), the nuclear as opposed to the cytoplasmic thread-work. (Flemming, 1882.)

Karyomito'sis (xapvov, nut, nucleus; see Mitosis), mitosis. (Flemming, 1882.)

L'ryon (xapvov, nut, nucleus), the cell-nucleus. (Hackel, 1891.) L'ryoplasm (Kapvov, nut, nucleus ; 7r\d<Tfia, a thing formed), nucleoplasm. The nuclear as opposed to the cytoplasmic substance. (Flemming, 1882.) t'ryosome (tcdpvov, nut, nucleus; ctu/uta, body). 1. Nucleoli of the *• net-knot " type, staining with nuclear dyes, as opposed to plasmosomes or true nucleoli. (Ogata, 1883.) 2. The same as chromosome. (Platner, 1886.) 3. Caryosome. The cell-nucleus. (Watase, 1894.)

[Karyo'ta] (napvov, nut, nucleus), nucleated cells. (Flemming, 1882.)

Karyothe'ca (Kapvov, nut, nucleus ; Orjurj, case, box), the nuclear membrane. (Hackel, 1891.) li'noplasm (klvuv, to move* irXavpa, a thing formed), nearly equivalent to archoplasm, but used in a broader sense to denote in general the more active elements of protoplasm from which arise fibrillar the substance of cilia, and (in plants) the peripheral " Hautschicht " from which the membrane is



formed; opposed to the " trophoplasm " or nutritive plasm. (Strasburger, 1892.)

[Lanthanin] (\avOdv€iv, to conceal), equivalent to oxychromatin. (Heidenhain, 1892.)

Leucoplaa'tids (acvkos, white; irAooros, form), the colourless plastids of plantcells from which arise the starch-formers (amyloplastids), chloroplastids, and chromoplastids. (Schimper, 1883.)

Li'nin (linum, a linen thread), the substance of the " achromatic " nuclear reticulum. (Schwarz, 1887.)

Lininoplast, the true nucleolus or plasmosome. (Eisen, 1899.)

Macrocentroaome, a term applied to the 4 * centrosome " in Boverfs sense, i.e. to the larger body in which lies the central granule. (Ziegler, 1898.) Probably synonymous with entosphere.

Maturation, the final stages in the development of the germ-cells. More specifically, the process by which the reduction of the number of chromosomes is effected.

Metakine'sis (see Metaphaae) (furd, beyond (/>. further) ; kiwtjctk;, movement), the middle stage of mitosis, when the chromosomes are grouped in the equatorial plate. (Flemming, 1882.)

Metanu'cleus, a term applied to the nucleolus after its extrusion from the germinal vesicle. (Hacker, 1892.)

Metaphase, the middle stage of mitosis during which occurs the splitting of the chromosomes in the equatorial plate. (Strasburger, 1884.)

Met'aplasm (/xera, after, beyond; irAac/Aa, a thing formed), a term collectively applied to the lifeless inclusions (deutoplasm, starch, etc.) in protoplasm as opposed to the living substance. (Hanstein, 1868.)

Micella, one of the ultimate supra-molecular units of the cell. (Nageli, 1884.)

Microcentrosome, equivalent to the central granule or centriole of Boveri. (Ziegler, 1898.)

Microcen'trum, the centrosome or group of centrosomes united by a " primary centrodesmus," forming the centre of the astral system. (Heidenhain, 1894.)

Mi'cropyle (fwcpo^, small; wvkq, orifice), the aperture in the egg-membrane through which the spermatozoon enters. [First applied by Turpin, in 1806, to the opening through which the pollen-tube enters the ovule. /. Robert Brown.]

Microsome (juicpo?, small ; ow/ua, body), the granules as opposed to the groundsubstance of protoplasm. (Hanstein, 1880.)

Microsphere, the central region of the aster (centrosphere) at the centre of which lie the centrosomes. (Kostanecki and Siedlecki, 1896.)

Middle-piece, that portion of the spermatozoon lying behind the nucleus at the base of the flagellum. (Schweigger-Seidel, 1865.)

Mid-body ("Zwischenkbrper"), a body or group of granules, probably comparable with the cell-plate in plants, formed in the equatorial region of the spindle during the anaphases of mitosis. (Flemming, 1890.)

Mi'tome (/u'rayia, from /u'ro?, a thread), the reticulum or thread-work as opposed to the ground-substance of protoplasm. (Flemming, 1882.)

[Mitoschi'ais (/u'tos, thread ; <rxi'£civ, to split), indirect nuclear division; mitosis. (Flemming, 1882.)

Mitosis (furoq, a thread), indirect nuclear division typically involving: a, the formation of an amphiaster; 6, conversion of the chromatin into a thread (spireme) ; c, segmentation of the thread into chromosomes ; d, splitting of the chromosomes. (Flemming, 1882.)

Mi'tosome (furos, a thread ; cra>/xa, body), a body derived from the spindle-fibres


of the secondary spermatocytes, giving rise, according to Platner, to the middle-piece and the tail-envelope of the spermatozoon. Equivalent to the Ne benkern of La Valette St. George. (Platner, 1889.)

Nebenkern (Paranucleus), a name originally applied by Biitschli (1871) to an extranuclear body in the spermatid ; afterwards shown by La Valette St. George and Platner to arise from the spindle-fibres of the secondary spermatocyte. Since applied to many forms of cytoplasmic bodies (yolk-nucleus, etc.) of the most diverse nature.

Nuclear plate. 1. The equatorial plate. (Strasburger, 1875.) 2. The partition-wall which sometimes divides the nucleus in amitosis.

Nuclein, the chemical basis of chromatin ; a compound of nucleinic acid and albumin or albumin radicles. (Miescher, 1871-)

Nucleinic or nucleic acid, a complex organic acid, rich in phosphorus, and an essential constituent of chromatin.

Nucleo-albumin, a nuclein having a relatively high percentage of albumin. Distinguished from nucleo-proteids by containing paranucleinic acid which yields no xanthin-bodies.

[Nucleoohyle'ma] (xvAos, juice), the ground-substance of the nucleus as opposed to that of the cytoplasm. (Strasburger, 1882.)

Nucleohy'aloplasma (see Hyaloplasm), the achromatic substance (linin) in which the chromatin-granules are suspended. (Strasburger, 1882.)

Nucleomi'crosomes (see Microsome), the nuclear (chromatin) granules as opposed to those of the cytoplasm. (Strasburger, 1882.)

Nucleoplasm. 1. The reticular substance of the (egg-) nucleus. (Van Beneden, 1875.) 2. The substance of the nucleus as opposed to that of the cellbody or cytoplasm. (Strasburger, 1882.)

Nucleo-pro'teid, a nuclein having a relatively high percentage of albumin. May be split into albumin and true nucleinic acid, the latter yielding xanthin-bodies.

GSde'matin (otS^/ua, a swelling), the granules or microsomes of the nuclear groundsubstance. (Reinke, 1893.)

O'Scyte (Ovocyte) (o>ov. egg; kvtos, hollow (a cell)), the ultimate ovarian egg before formation of the polar bodies. The primary oocyte divides to form the first polar body and the secondary oocyte. The latter divides to form the second polar body and the mature egg. (Boveri, 1891.)

Oogen esis. Ovogenesis (aidy, egg ; yc'vco-is, origin), the genesis of the egg after its origin by division from the mother-cell. Often used more specifically to denote the process of reduction in the female.

Oogonium, Ovogonium (o>ov, egg ; yovrj, generation). 1 . The primordial mothercell from which arises the egg and its follicle. (Pfluger.) 2. The descendants of the primordial germ-cell which ultimately give rise to the oocytes or ovarian eggs . ( Bo veri, 1 89 1 . )

Ookinesis (a)dv, egg; ku^o-is, movement), the mitotic phenomena of the egg during maturation and fertilization. (Whitman, 1887.)

O'vocentre, the egg-centrosome during fertilization. (Fol, 1891.)

Oxychi o'matin (o£ vs, acid ; see Chromatin), that portion of the nuclear substance stained by acid tar-colours. Equivalent to " linin " in the usual sense. (Heidenhain, 1894.)

Pangen'esis (7ras (7rav-), all; •ycyecris, production), the theory of gem mules, according to which hereditary traits are carried by invisible germs thrown off by the individual cells of the body. (Darwin, 1868.)

Pangens (7ra« (7rav-), all ; -yev^s, producing), the hypothetical ultimate supra-molecular units of the idioplasm, and of the cell generally. Equivalent to gemmules, micellae, idioblasts, biophores, etc. (De Vries, 1889.)


Farachro'matin (see Chromatin), the achromatic nuclear substance (linin of Schwarz) from which the spindle-fibres arise. (Pfitzner, 1883.)

Parali'nin (see Linin), the nuclear ground-substance or nuclear sap. (Schwarz, 1887.)

Parami'tome (see Mitome), the ground-substance or interfilar substance of protoplasm, opposed to mitome. (Flemming, 1892.)

Paranu'clein (see Nuclein), the substance of true nucleoli or plasmosomes. Pyrenin of Schwarz. (O. Hertwig, 1878.) Applied by Kossel to "nucleins" derived from the cytoplasm. These are compounds of albumin and paranucleic acid which yields no xanthin-bodies.

Paranucleus (see Nebenkern).

Paraplasm (wapd, beside ; irAac/io, something formed), the less active portion of the cell-substance. Originally applied by Kupffer to the cortical region of the cell (exoplasm), but now often applied to the ground-substance. (Kupffer,

1875.) Periplast (irtpu around; ir\aor6s y form). 1. The peripheral part of the cell,

including those parts outside the nucleus or "endoplast." (Huxley, 1853.)

2. A term somewhat vaguely applied to the attraction-sphere. The term

daughter-periplast is applied to the centrosome. (Vejdovsky, 1888.)

Perisphere (ircpt, around), a term applied to the outer region of the attractionsphere in nerve-cells, and opposed to an inner " centrosphere." (Lenhoss£k, 1895.)

Plasmocytes (irXdo-fjuL, kvtos), colourless blood-corpuscles supposed to be free attraction-spheres. (Eisen, 1897.)

Plasmosphere, the same as Perisphere.

Plaa'mosome (7rAaoyza, something formed (i.e. protoplasmic) ; o-w/tia, body), the true nucleus, distinguished by its affinity for acid tar-colours and other " plasmastains." (Ogata, 1883.)

Pla'some (irXda-fm, a thing formed; crwfia, body), the ultimate supra-molecular vital unit. See Biophore, Pangen. (Wiesner, 1890.)

Plas'tid (irAasros, form). 1. A cell, whether nucleated or non-nucleated. (Hackel. 1866.) 2. A general term applied to permanent cell-organs (chloroplasts, etc.) other than the nucleus and centrosome. (Schimper, 1883.)

Plas'tidule, the ultimate supra-molecular vital unit. (Elssberg, 1874; Hackel, 1876.)

Plas'tin, a term of vague meaning applied to a substance related to the nucleoproteids and nucleo-albumins constituting the linin-network (Zacharias) and the cytoreticulum (Carnoy). (Reinke and Rodewald, 1881.)

Pluri'valent (p/us, more; vaUre. to be worth), applied to chromatin-rods that have the value of more than one chromosome sensu strictu. (Hacker, 1892.)

Polar bodies (Polar globules), two minute cells segmented off from the ovum before union of the germ-nuclei. (Disc, by Carus, 1824; so named by Robin, 1862.)

Polar corpuscle, the centrosome. (Van Beneden, 1876.)

Polar rays (Polradien), a term sometimes applied to all of the astral rays as opposed to the spindle-fibres, sometimes to the group of astral rays opposite to the spindle-fibres.

Pole-plates (End-plates), the achromatic spheres or masses at the poles of the spindle in the mitosis of Protozoa, probably representing the attraction-spheres. (R. Hertwig, 1877.)

Polyspermy, the entrance into the ovum of more than one spermatozoon.

[Prochro'matin] (see Chromatin), the substance of true nucleoli, or plasmosomes. Equivalent to paranuclei of O. Hertwig. (Pfitzner, 1.883.)


Pronuclei, the germ-nuclei during fertilization ; i.e. the egg-nucleus (female pronucleus) after formation of the polar bodies, and the sperm-nucleus (male pronucleus) after entrance of the spermatozoon into the egg. (Van Bexedex,


[Prothy'alosome] (see Hyalosome), an area in the germinal vesicle (of A scans) by which the germinal spot is surrounded, and which is concerned in formation of the first polar body. (Van Beneden, 1883.)

Pro'toblast (7rpa>ros, first; /JAooros, a germ). 1. A naked cell, devoid of a membrane. (Kolliker.) 2. A blastomere of the segmenting egg which is the parent-cell of a definite part or organ. (Wilson, 1892.)

Protoplasm (7rpo>Tos, first ; irXdtrfw^ a thing formed or moulded) . The active or " living " cell-substance. By all earlier and some present writers applied only to the substance of the cell-body (equivalent to Strasburger's cytoplasm). By many later writers applied to the entire active substance of the cell (karyoplasm plus cytoplasm). (Purkinje, 1840; H. von Mohl, 1846.)

Protoplast (irpwros, first; wAixotos, formed). 1. The protoplasmic body of the cell, including nucleus and cytoplasm, regarded as a unit. Nearly equivalent to the energid of Sachs. (Hanstein, 1880.) 2. Used by some authors synonymously with plastid.

[Pseudochro'matln] (see Chromatin), the same as prochromatin. (Pfitzner, 1886.)

Pseudonu'clein (see Nuclein), the same as the paranuclein of Kossel. (Ham MARSTEN, 1894.)

Pseudo-reduction, the preliminary halving of the number of chromatin-rods as a . prelude to the formation of the tetrads and to the actual reduction in the number

of chromosomes in maturation. (Ruckert. 1894.) Pyre'nin (jrvprfv, the stone of a fruit ; i.e. relating to the nucleus), the substance of

true nucleoli. Equivalent to the paranuclein of Hertwig. (Schwarz, 1887.) Pyre'noid (wvprjv, the stone of a fruit ; like a nucleus), colourless plastids (leuco plastids). occurring in the chromatophores of lower plants, forming centres for

the formation of starch. (Schmitz, 1883.) Reduction, the halving of the number of chromosomes in the germ-nuclei during

maturation. Sarcode (<rap£, flesh). The protoplasm of unicellular animals. (Du Jardin.

1835) Sertoli-cells, the large, digitate, supporting, and nutritive cells of the mammalian

testis to which the developing spermatozoa are attached. (Equivalent to u spermatoblast " as originally used by Von Ebner, 1871.)

Spermatid (oTrc'p/uLa, seed), the final cells which are converted without further division into spermatozoa ; they arise by division of the secondary spermatocytes or " SamenmUtterzellen. ,, (La Valete St. George, 1886.)

Spermatoblasts (<nrcp/Lia, seed; yftAaoros, germ), a word of vague meaning, originally applied to the supporting cell or Sertoli-cell, from which a group of spermatozoa was supposed to arise. By various later writers used synonymously with spennatid. (Von Ebner, 1871.)

Sper'matocyst (cnrc'p/ua, seed : kvottis, bladder), originally applied to a group of sperm-producing cells ("spermatocytes ■ 1 ), arising by division from an "Ursamenzelle" or "spermatogonium.'" (La V alette St. George, 1876.)

Sper'matocyte (oircp/ia, seed; kvtos, hollow (a cell)), the cells arising from the spermatogonia. The primary spermatocyte arises by growth of one of the last generation of spermatogonia. By its division are formed two secondary spermatocytes, each of which gives rise to two spermatids (ultimately spermatozoa). (La Valette St. George, 1876.)


[Sperm atogem'ma] (cnrcp/ia, seed ; gemma, bud), nearly equivalent to spermatocyst. Differs in the absence of a surrounding membrane. [In mammals, La Valette St. George, 1878.]

Spermatogenesis (cnrcppo, seed; ycrccri?, origin), the phenomena involved in the formation of the spermatozoon. Often used more specifically to denote the process of reduction in the male.

Spermatogo'nium (" Ursamenzelle ") (cnrcp/ia, seed ; yovrj, generation), the descendants of the primordial germ-cells in the male. Each ultimate spermatogonium typically gives rise to four spermatozoa. (La Valette St. George, 1876.)

Bpermatome'rites (cnrcppa, seed ; /icpos, a part), the chromatin-granules into which the sperm-nucleus resolves itself after entrance of the spermatozoon. (In Petromyzon, Bohm, 1887.)

Bper'matosome (cnrcp/ia, seed; crw/ia, body), the same as spermatozoon. (La Valette St. George, 1878.)

Spermatozo Id (see Spermatozoon), the ciliated paternal germ-cells in plants. The word was first used by von Siebold as synonymous with spermatozoon.

Spermatozoon (<r7rcppo, seed ; (<£ov, animal), the paternal germ-cell of animals. (Leeuwenhoek, 1677.)

Sperm-nucleus, the nucleus of the spermatozoon ; more especially applied to it after entrance into the egg before its union with the egg-nucleus. In this sense equivalent to the " male pronucleus " of Van Beneden. (O. Hertwig,

1875.) Bper'mocentre, the sperm-centrosome during fertilization. (Fol, 1891.) Spi'reme (cnrctpi/fia, a thing wound or coiled ; a skein), the skein or " Knauel "

stage of the nucleus in mitosis, during which the chromatin appears in the form

of a thread, continuous or segmented. (F lemming, 1882.) Spon'gioplasm (cnroyytov, a sponge ; irAacrpa, a thing formed), the cytoreticulum.

(Leydig, 1885.) Ste'reoplasm (orcpco?, solid), the more solid part of protoplasm as opposed to the

more fluid " hygroplasm." (Nageli, 1884.) Substantia hyalina, the protoplasmic ground-substance or "hyaloplasm."

(Leydig, 1885.) Substantia opaca, the protoplasmic reticulum or " spongioplasm." (Leydig,

1885.) Synap'sis (<rwa7rrci>, to fuse together). A stage in the nucleus preceding the first

maturation-division, characterized by the massing of the chromatin at one side

of the nucleus. From it the chromatin-masses emerge in the reduced number.

(Moore, 1895.) Te'loblast (tcAos, end : /JAaoros, a germ), large cells situated at the growing end

of the embryo (in annelids, etc.), which bud forth rows of smaller cells. (Whitman, Wilson, 1887.) Telole'cithal (tcXos, end ; AcVctlo?, yolk), that type of ovum in which the yolk is

mainly accumulated in one hemisphere. (Balfour, 1880.) Telophases, Telokine'sis (rcAo?, end), the closing phases of mitosis, during

which the daughter-nuclei are re-formed. (Heidenhain, 1894.) To'noplasts (rovos, tension ; wXaoros, form), plastids from which arise the vacuoles

in plant-cells. (De Vries, 1885.) Trophoplasm (rpo<t>^ nourishment; 7rAan-pa). 1. The nutritive or vegetative

substance of the cell, as distinguished from the idioplasm. (Nageli, 1884.)

2. The active substance of the cytoplasm other than the "kinoplasm " or archo plasm. (Strasburger, 1892.) Tro'phoplasts (Tpotjrrj, nourishment ; trAooros, form), a general term, nearly equiv


alent to the "plastids" of Schimper, including "anaplasts" (amyloplasts),

"autoplasts" (chloroplasts), and chromoplasts. (A. Meyer, 1882-83.) Yolk-nucleus, a word of vague meaning applied to a cytoplasmic body, single or

multiple, that appears in the ovarian egg. [Named " Dotterkern " by Carus.

1850.) Zy'gote or Zy'gospore (£vyw, a yoke), the cell produced by the fusion of two

conjugating cells or gametes in some of the lower plants.



The following list includes only the titles of works actually referred to in the text and those immediately related to them. For more complete bibliography the reader Is referred to the literature-lists in the special works cited, especially the following. For reviews of the early history of the cell-theory see Remak's Untersuchungen ( ? 50-'55), Huxley on the Cell-theory ("53), Sach's History of Botany and Tyson's Cell-doctrine O78) . An exhaustive review of the earlier literature on protoplasm, nucleus, and cell-division will be found in Flemming's Zellsubstanz ('82), and a later review of theories of protoplasmic structure in BUtschli's Protoplasma ('92) and in Fischers Fixierung* etc., des Protoplasmas C99). The earlier work on mitosis and fertilization is very thoroughly reviewed in Whitman's Clepsine ('78), Fol's Hhiogenie ('79)« an d Mark's Umax ("81). For more recent general literature-lists see especially Hertwig's Zelle und Gewcbe ('93, '98), Yves Delage (95), Henneguy's Cellule ("96), Hacker's Praxis und Theorie der Zelle n und Befruchtungslehre ('99), and the admirable reviews by Flemming, Boveri, RUckert, Meves, Roux, and others in Merkel and Bonnet's Ergebnisse ('9 1-98).

The titles are arranged in alphabetical order, according to the system adopted in Minot's Human Embryology. Each author's name is followed by the date of publication (the first two digits being omitted, except in case of works published before the present century), and this by a single number to designate the paper, in case two or more works were published in the same year. For example, Boverl, Th., '87. 2, denotes the second paper published by Boveri in 1887.

In order to economize space, the following abbreviations are used for the journals most frequently referred to : —


A. A. Anatomischcr Anzeiger.

A. B. Archives dc Biologic

A. A. P. Archiv fur Anatomie und Physiologic

A . m. A. Archiv fur mikroscopische Anatomie.

A. Entwm. Archiv fur Entwicklungsmechanik.

B. C. Biologisches Ccntralblatt.

C. R. Comptes Rendus.

/. M. Journal of Morphology.

J. w. Bo/. Jahrhuch fur wissenschaftliche Botanik.

J. Z. Jenaische Zeitschrift.

M. A. Muller's Archiv.

M.J. Morphologisches Jahrbuch.

Q.J. Quarterly Journal of Microscopical Science.

Z. A. Zoologischer Anzeiger.

Z. w. Z. Zeitschrift fur wissenschaftliche Zoologie.

ALBRECHT, B., '98. Untersuchungen zur Structur des Seeigeleies : Sitzb. Ges.

Aforph. P/iys. MYmchen.. 3. — Altman, R., *86. Studien iiber die Zelle, I. : Leipzig.

— Id., '87. Die Genese der Zellen: Leipzig. — Id., '89. Cber Nucleinsaure : A.

A. P., p. 524. — Id., '90, '94. Die Elementarorganismen und ihre Beziehung zu

2G 449


den Zellen : Leipzig. — Amelung, B., -93. Uber mittlere Zellgrosse : Flora* p. 176.

— Andrews, B. A., 98, 1. Filose Activities in Metazoan Eggs : Zool. Bull., II., 1.

— Id., '98, 2. Activities of Polar Bodies of Cerebratulus : Arch. Entivm., VI., 2. — Andrews, Q-. P., '97. The Living Substance as Such and as Organism : J. M.* XII., 2, Suppl. — Arnold, J., '79. Uber feinere Struktur der Zellen, etc. : Virchows Arch.* 1879. (See earlier papers.) — Atkinson, O. P., '99. Studies on Reduction in Plants : Bo/. Gaz.* XX VIII., 1, 2. — Auerbach, L., '74. Organologische Studien :

.Breslau. — Id., '91. Uber einen sexuellen Gegensatz in der Chromatophilie der Keimsubstanzen : Sitzungsber . der Konigl. preuss. A had. d. Wiss. Berlin* XXXV.

— Id. "96. Untersuchungen liber die Spermatogenese von Paludina : J. Z. % XXX.

VON BAER, C. B., '28, '37. Uber Entwickelungsgeschichte der Thiere. Beobachtung und Reflexion: I. Konigsberg* 1828; II. 1837. — Id., -34. Die Metamorphose des Eies der Batrachier : Mutter's Arch. — Balbiani, B. O.. '61. Recherches sur les ph^nomenes sexuels des Infusoires : Journ. de la Phys.* IV. — Id., *64. Sur la constitution du germe dans Toeuf animal avant la fecondation: C. R.* LVIII. — Id., '76. Sur les phdnomenes de la division du noyau cellulaire: C. R.* XXX., October, 1876. — Id., '81. Sur la structure du noyau des cellules salivares chez les larves de Chironomus : Z. A.* 1881, Nos. 99, 100. — Id., '89. Recherches experimen tales sur la merotomie des Infusoires cilies : Recueil Zool. Suisse* January, 1889.

— Id., '91, 1. Sur les regenerations successives du peristome chez les Stentors et sur le r6ie du noyau dans ce phe'nomene : Z. A.* yj2, 373. — Id., *91, 2. Sur la structure et division du noyau chez les Spirochona gemmipara: Ann. d. Micrographie. — Id., *93. Centrosome et Dotterkern : Journ. de Fanat. el de la physiol.* XXIX.— Balfour, P. M., '80. Comparative Embryology: I. 1880.— Ballowitz, '88-'91. Untersuchungen liber die Struktur der Spermatozoen : 1 . (birds) A. m. A.. XXXII.. 1888; 2. (insects) Z.w.Z.* LX., 1890; 3. (fishes, amphibia, reptiles) A. m. A., XXXVI., 1890; 4. (mammals) Z. w. Z.* 1891. — Id., '89. Fibrillare Struktur und Contractilitat : Arch. ges. Phys.* XLVI. — Id., '91, 2. Die inncre Zusammensetzung des Spermatozoenkopfes der Saugetiere : Centralb.f. Phys.. V. — Id., '95. Die Doppelspermatozoa der Dytisciden : Z. w. Z.* XLV.. 3. — Id., '97. Uber Sichtbarkeit und Aussehen der ungetarbten Centrosomen in ruhenden Gewebszellen : Z. w. Mic. XIV. — Id., '98. Zur Kenntniss der Zellsphare: Arch. Anal. Phys.* 98, II., III. — Van Bambeke, C, '93. Elimination dWments nucleaires dans l'oeuf ovarien de Scorpa^na scrofa: A. B.* XIII.. 1. — Id., '96. De Pemploi du terme Protoplasma : Bull. Soc. Beige. Mic, XXII. — Id., '97. A propos de la delimitation cellulaire: Ibid., XXIII. — Id., '98. Recherches sur roocyte de Pholcus phalangioides : --/. />'., XV. — De Bary, '58. Die Conjugaten. — Id., '62. Uber den Ban und das VVesen der Zelle: Flora, 1862. — Id., '64. Die Mycetozoa: 2d Ed., Leipzig. — Barry, M. Spermatozoa observed within the Mammiferous Ovum : Phil. Trans., 1843. — Beale, Lionel S., '61. On the Structure of Simple Tissues of the Human Body : London. — B^ champ and Bstor, '82. De la constitution ele'mentaire des tissues: Mont pettier. — Belajeff, W., '89. Mittheilung Uber Bau und Entwicklung der Spermatozoiden : Bcr. D. Bot. Ges. — Id., '92. 1. Uber den Bau und die Entwicklung der Antherozoiden, I., Characeen. — Id., '92. 2. Uber die Karyokinesis in den Pollenmutterzellen bei luirix und Fritillaria: Sitzb. li'arsch. Naturf. Ges. — Id., '94, 1. Zur Kenntniss der Karyokinese bei den Pfianzen: Flora. 1894, Erganzungsheft. — Id., '94,2. Uber Bau und Entwicklung der Spermatozoiden der Pfianzen : Flora, LIV. — Id., '97, 1. Uber den Nebenkern in Spermatogenen Zellen und die Spermatogenese bei den Farnkrauten : Ber. I). Bot. Ges.* XV. — Id., '97, 2. Uber die Spermatogenese bei den Schachtelhalmen : Ibid. — Id., '97, 3. Uber die Aehnlichkeit einiger Erscheinungen in der Spermatogenese bei Thieren und Pfianzen: Ibid. — Id., '97, 4. Einige Streit


fragen in den Untersuchungen liber die Karyokinese: Ibid. — Id., '98, 1. Uber die Reductionstheilung des Pflanzenkerns : Ibid., XVI. — Id., '98, 2. t)ber die Cilienbildrfer in den spermatogenen Zellen : Ibid. — Id., '99. Uber die Centrosomen in den spermatogenen Zellen: Ibid., XVII., 6. — Benda, C, *87. Untersuchungen liber den Bau des funktionirenden Samenkenkanalchens einiger Saugethiere: A. m. A. — Id., '93. Zellstrukturen und Zelltheilungen des Salamanderhodens : Verh. d. Anat. Ges., 1893. — Van Beneden, B., '70. Recherches sur la composition et la signification de Poeuf : Mhn. cour. de VAc. roy. d. S. de Belgique, 1870. — Id., '75. La maturation de Toeuf, la fe'condation et les premieres phases du de'veloppement embryonnaire des mammiferes d'aprcs des recherches faites chez le lapin: Bull. Ac. roy. de Belgique, XI. — Id., '76, 1. Recherches sur les Dicye'mides: Bull. Ac. roy. Belgique* XLI., XLII. — Id., '76, 2. Contribution a Thistoire de la vdsicule germinative et du premier noyau embryonnaire : Ibid., XLI. ; also Q.J., XVI. — Id., '83. Recherches sur la maturation de l'oeuf, la fe'condation et la division cellulaire: A. B., IV. — Van Beneden and Julin. '84, 1. La segmentation chez les Ascidiens et ses rapports avec l'organisation de la larve: Ibid.,V. — Id., '84, 2. La spermatogenese chez TAscaride mdgaloc^phale : Bull. Ac. roy. Belgique, 3me ser.. VII. — Van Beneden, E., et Neyt, A.. '87. Nouvelles recherches sur la fdcondation et la division mitosique chez TAscaride me'galoce'phale : Ibid., 1887. — Bergh, R. S., '89. Recherches sur les noyaux de TUrostyla : A. B. IX. — Id., '94. Vorlesungen liber die Zelle und die einfachen Gewebe : Wiesbaden. — Id., '95. Uber die relativen Theilungspotenzen einiger Embryonalzellen : A. Entm., II., 2. — Bernard, Claude. Lecons sur les Phe'nomenes de la Vie: 1st Ed. 1878, 2d Ed. 1885, Paris. — Berthold, 0^86. Studien Uber Protoplasma-mechanik : Leipzig. — Bickford, E. E., '94. Notes on Regeneration and Heteromorphosis of Tubularian Hydroids: /. J/., IX., 3. — Biondi. D., '85. Die Entwicklung der Spermatozoiden : A. m. A., XX V. — Blanc, H., -93. Etude sur la fe'condation de Toeuf de la truite : Ber. Naturforsch. Ges. zu Freiburg, VIII. — Blochmann,F.,'87, 2. Uber die Richtungskorper bei lnsekteneiern : M. /., XII. — Id., '88. Uber die Richtungskorper bei unbefruchtet sich entwickelnden Insekteneiern : Verh.naturh. wed. Ver. Heidelberg N. F., IV., 2. — Id., *89. Uber die Zahl der Richtungskorper bei befruchteten und unbefruchteten Bieneneiern : M.J. — Id., '94. Uber die Kerntheilung bei Euglena : B. C.„ X I V. — Btthm, A.. '88. Uber Reifung und Befruchtung des Eies von Petromyzon Planeri : A. ///. A., XXXII. — Id.. '91. Die Befruchtung des Forelleneies : Sitz.-Ber. d. Ges. f. Morph. u. Phys. Munchen, VII. — Boll, Pr., '76. Das Princip des Wachsthums : Berlin. — Bonnet, C 1762. Considerations sur les Corps organ isds : Amsterdam. — Born, O., ^85. Uber den Einfluss der Schvvere auf das Froschei : A. m. A., XXIV. — Id., "94. Die Structur des Keimblaschens im Ovarialei von Triton t«niatus : A. m. A.. XLIII. — Bourne, O. C, '95. A Criticism of the Cell-theory ; being an Answer to Mr. Sedgwick's Article on the Inadequacy of the Cellular Theory of Development; (J. J. XXXVIII., 1— Boveri, Th., '86. Uber die Bedeutung der Richtungskorper : Sitz.-Ber. Ges. Morph. u. Phys. Miinchen, II. — Id., '87, 1. Zellenstudien. Heft I. ; /. Z., XXI. —Id., '87, 2. Uber die Befruchtung der Eier von Ascaris me^alocephala : Sitz.-Ber. Ges. Morph. Phys. Miinchen, III. — Id., '87, 2. Uber den Anteil des Spermatozoon an der Teilung des Eies: Sitz.-Ber. Ges. Morph. Phys. Miinchen* III., 3. — Id., '87,3. Uber Differenzierung der Zellkerne wahrend der Furchung des Eies von Ascaris meg.: A. A., 1887. — Id., '88, 1. Uber partielle Befruchtung : Sitz.-Ber. Ges. Morph. Phys. Miinchen, IV., 2. — Id., '88. 2. Zellenstudien, II. : /. Z., XXII. — Id., '89. Ein geschlechtlich erzeugter Organismus ohne mlitterliche Eigenschaften : Sitz.-Ber. Ges. Morph. Phys. Miinchen. V. Trans, in Am. A r at., March, '93. — Id., '90. Zellenstudien, Heft III . : J. Z., XXIV. — Id., '91. Befruchtung: Merkel und Bonnets Ergebnisse, I. — Id.,


  • 95, 1. Uber die Befruchtungs- und Entwickelungsfahigkeit kernloser Seeigel-Eier,

etc. : A. Entwm. II., 3. — Id., '95, 2. tlber das Verhalten der Centrosomen bei der Befruchtung des Seeigeleies, nebst allgemeinen Bemerkungen iiber Centrosomen und Verwandtes : Verh. d. Physikal.-med. Gesellschaft zu Wurzburg, N. F., XXIX., 1. — Id., '96. Zur Physiologie der Kern- und Zellteilung: Sitsb. Phys.Med. Ges. Wurzburg. — Braem, P., '93. Das Prinzip der organ bilden den Keimbezirke und die entwicklungsmechanischen Studien von H. Driesch : B. C, XI 11., 4, 5. — Brandt, H., '77. Ober Actinosphaerium Eichhornii: Dissertation, Halle, 1877. — Brass, A., 7 83-4. Die Organisation der thierischen Zelle : Halle.— Brauer, A., '92. Das Ei von Branchipus Grubii von der Bildung bis zur Ablage: Abh. preuss. Akad. Wiss., '92. — Id., '93,1. Zur Kenntniss der Reifung des parthenogenetisch sich entwickelnden Eies von Artemia Salina: A. m. A., XLIII.— Id., '93, 2. Zur Kenntniss der Spermatogenese von Ascaris megalocephala : A. m. A., XL1I. — Id., '94. tJber die Encystierung von Actinosphaerium Eichhornii: Z. w. Z., LVIII., 2. — Braus, '95. Uber Zellteilung und Wachstum des Tritoneies: /. Z., XXIX. — Brooks, W. K., '83. The Law of Heredity: Baltimore. Brown, H. H. f '85. On Spermatogenesis in the Rat : Q. /., XXV. — Brown, Robert, '33. Observations on the Organs and Mode of Fecundation in Orchideae and Asclepiadese : Trans. Linn. Soc, 1833. Brticke, C, '61. Die Elementarorganismen : Wiener Sitzbcr., XLIV., 1861. Brunn,M. von, '89. Beitrage zur Kenntniss der Samenkorper und ihrer Entwickelung bei Vogeln und Saugethieren : A. m. A., XXXIII. — De Bruyne, C, '95. La sphere attractive dans les cellules fixes du tissu conjonctif: Bull. Acad. Sc. de Belgian e, XXX. — Biirger, O., '91. Uber Attractionsspharen in den Zellkorpern einer Leibesflussigkeit : A. A., VI. — Id., '92. Was sind die Attractionsspharen und ihre Centralkorper? A. A., 1892. — BUtschli, O., '73. Beitrage zur Kenntniss der freilebenden Nematoden: Nova acta acad. Car. I^eopold, XXXVI. — Id., '75. Vorlaufige Mitteilungen iiber Untersuchungen betreflfend die ersten Entwickelungsvorgange im befruchteten Ei von Nematoden und Schnecken : Z. w. Z., XXV. — Id., '76. Studien iiber die ersten Entwickelungsvorgange der Eizelle, die Zellteilung und die Konjugation der Infusorien : Abh. des Senckcnb. Naturforscher-Ges.. X. — Id., '85. Organisationsverhaltnisse der Sog. Cilioflagellaten und der Noctiluca: M. /., X. — Id., '90. t*ber den Bau der Bakterien, etc.: Leipzig. — Id., '91. tjber die sogenannten Centralkorper der Zellen und ihre Bedeutung: Verh. Naturhist. Med. Ver. Heidelberg 1891. — Id., '92, 1. tlber die kiinstliche Nachahmung der Karyokinetischen Figuren : /bid., N. F\, V. — Id., '92, 2. Untersuchungen iiber mikroskopische Schaume und das Protoplasma (full review of literature on protoplasmic structure) : Leipzig {En^eltnann). — Id., '94. Vorlaufige Berichte iiber fortgesetzte Untersuchungen an Gerinnungsschaumen, etc. : Verh. Naturhist. Ver. Heidelberg V. — Id., '96. Weitere Ausfuhrungen iiber den Bau der Cyanophyceen und Bakterien : Leipzig. — Id., '98. Untersuchungen iiber Strukturen : Leipzig (Engebnann).

CALKINS, O. N., '95, 1. Observations on the Yolk-nucleus in the Eggs of Lumbricus : Trans. N.Y. Acad. So'., June, 1895. — Id., '95, 2. The Spermatogenesis of Lumbricus : /. A/., XL, 2. — Id., '97. Chromatin-reduction and Tetradformation in Pteridophytes : Bull. Torrey Bot. Club, XXIV. — Id., *98, 1. The Phylogenetic Significance of Certain Protozoan Nuclei : Ann. N V. Acad. Sci.. Xl«  16. —Id., '98, 2. Mitosis in Noctiluca: Ginn & Co., Boston, also/. /!/., XV., 3.— Calberla, E., '78. Der Befruchtungsvorgang beim Ei von Petromyzon Planeri: Z.w.Z., XXX. — Campbell, D. H., '88-9. On the Development of Pilularia globulifera : Ann. Bot.. II. — Carnoy, J. B., '84. La biologie cellulaire : Lierre. — Id., '85. La cytodidrese des Arthropodes : La Cellule. I. — Id., '06. La cytodi£rese de Tceuf: La Cellule, III. — Id., '86. La ve'sicule germinative et les globules


polaires chez quelques Nematodes: La Cellule, III. — Id., '86. La segmentation de Toeuf chez les Nematodes: La Cellule* III., 1. — Carnoy and Le Bran, '97, 1, '98, '99. La vdsicule germinative et les globules polaires chez les Batraciens : La Cellule. XII, XIV, XVI. — Id., '97, 2. La fe'eondation chez l'Ascaris megalocephala : La Cellule* XIII. — Castle, W. E., '96. The Early Embryology of Ciona intestinalis : Bull. A/us. Comp. Zoo/., XXVII., 7. — Chabry, L., '87. Contributions a Tembryologie normale et pathologique des ascidies simples: Pan's. 1887.

— Child, C. M., '97. The Maturation and Fertilization of the Egg of Arenicola : Trans. N. Y. Acad. Sci.. XVI. — Chittenden, R. H., '94. Some Recent Chemicophysiological Discussions regarding the Cell: Am. Na/., XXVIII., Feb., 1894. — Chun, C, '90. Uber die Bedeutung der direkten Zelltheilung : Si/zb. Schr. Physik.Ofcon. Ges. K'dnigsberg. 1890. — Id., *92, 1. Die Dissogonie der Rippenquallen : Fes/schr. f. Leuckar/, Leipzig, 1892. — Id., '92, 2. (In Roux, '92, p. 55) : Verh. d. Ana/. Ges., VI., 1892. — Clapp, C. M., '91. Some Points in the Development of the Toad-Fish : /. A/.. V. — Clarke, J. Jackson, '95. Observations on various Sporozoa: Q.J., XXXVII., 3. — Coe, W. R., '99. The Maturation and Fertilization of the Egg of Cerebratulus : Zoo/.Jahrb., XII. — Cohn, Ferd., '51. Nachtrage zur Naturgeschichte des Protococcus pluvialis : Nova Ac/a. XXII. — Conklin, E. O., '94. The Fertilization of the Ovum : Biol. Lee/.. Marine Biol. Lab., Wood's Noll, Bos/on, 1894. — Id., '96. Cell-size and Body-size: Rep/, of Am. A/orph. Soc. Science. III., Jan. 10, 1896. — Id., *97, 1. Nuclei and Cytoplasm in the Intestinal Cells of Land Isopods : Am. Nat.. Jan. — Id., '97, 2. The Embryology of Crepidula : /. A/., XIII., 1.-— Id., '98. Cleavage and Differentiation: Wood's Noll Biol. Uc/ures. — Id., '99. Protoplasmic Movement as a Factor in Differentiation : Wood's Ho// Biol. Lec/ures. — Cramp ton, H. B., '94. Reversal of Cleavage in a Sinistral Gasteropod: Ann. N. Y. Acad. Sci., March, 1894. — Id., '97. The Ascidian HalfEmbryo: Ibid., June 19. — Id., '99. The Ovarian History of the Egg of Molgula: /. J/., XV., Suppl. — Crampton and Wilson, *96. Experimental Studies on Gasteropod Development (H. E. Crampton). Appendix on Cleavage and MosaicWork (E. B. Wilson) : A. En/wm.. III., 1. — Czermak, N., '99. Uber die Desintegration und die Reintegration des Kernkorperchens, etc. : A. A., XV., 22.

DARWIN, P., '77. On the Protrusion of Protoplasmic Filaments, etc. : Q. J. XVII. — Davis, B. M., '99. The Spore-mother-cell of Anthoceros: Bo/. Gaz., XXVIII., 2. — Debski, B., '97. Beobachtungen Uber Kerntheilung bei Chara: J. w. B., XXX.— Id., '98. Weitere Beobachtungen an Chara: Ibid., XXXII., 4.

— Delage, Yves, '95. La Structure du Protoplasma et les Theories sur l'hdre'dite' et les grands Problemes de la Biologie Gdndrale : Paris, 1895. — Id., '98. Embryons sans noyau maternel: C. R.. CXXVII., 15. — Id., '99. La fdcondation me'rogonique et ses rdsultats: C. R.. Oct. 23. — Demoor, J., '95. Contribution a Te'tude de la physiologie de la cellule (inddpendance fonctionelle du protoplasme et du noyau) : A. B., XIII. — Dendy, A., '88. Studies on the Comparative Anatomy of Sponges: Q.J.% Dec, 1888. — Dixon, H. H., '94. Fertilization of Pinus: Ann. Bo/., VIII. — Id., '96. On the Chromosomes of Lilium longliflorum : Proc. R. Ir. Ac, III. — Doflein, P. J., *97, 1. Die Eibildung bei Tubularia: Z. w. Z., LXII., 1. — Id., '97, 2. Karyokinesis des Spermakerus: A. m. A., L, 2. — Dogiel, A. S., '90. Zur Frage uber das Epithel der Harnblase : A. m. A., XXXV. — Driesch, H., '92, 1. Entwickelungsmechanisches : A. A., VII., 18. — Id. Entwicklungsmechanische Studien, I., II., 1892, Z. w. Z., LIU. ; 1 1 1. -VI., 1893, Ibid.. LV. ; VII.-X., 1893: A/itt. Zo'dl. St. Neapel. XL, 2.— Id., '94. Analytische Theorie der organischen Entwicklung: Leipzig. — Id., '95. 1. Von der Entwickelung einzelner Ascidienblastomeren : A. Entwm., L, 3. — Id., '95, 2. Zur Analysis der Potenzen embryonaler Organzellen: Ibid., II. — Id., '98,1. Uber den Organisation des


Eies: Entwm., IV. — Id.. '98, 2. Von der Beendigung morphogener Elementarprocesse: Arch. Entwm. , VI. — Id., '98, 3. Ueber rein-miitterliche Charaktere an Bastardlarven von Echiniden: Ibid., VII., i. — Id., '99. Die Localisation morphogenetischer Vorgange: Ibid., VIII., I. — Drieach and Morgan, '95, 2. Zur Analysis der ersten Entwickelungsstadien des Ctenophoreneies : Ibid.* II., 2.— Drtiner, L., '94. Zur Morphologie der Centralspindel : /. Z., XXVIII. (XXI.). — Id., '95. Studien iiber den Mechanismus der Zelltheilung: Ibid., XXIX., 2. — Dflsing, C, 1 84. Die Regulierung des Geschlechtsverhaltnisses : Jena, 1884.

VON EBNER, V., '71. Untersuchungen iiber den Bau der Samencanalchen und die Entwicklung der Spermatozoiden bei den Saugethieren und beim Menschen: Inst. Phys. u. Hist. Graz., 1871 (Leipzig). — Id., '88. Zur Spermatogenese bei den Saugethieren: A. m. A., XXXI. — Ehrlich, P., '79. Ober die specifischen Granulationen des Blutes: A. A. P. (Phys.), 1879, P- 573- — Bi»en, Gk, *97. Plasmocytes: Proc. Cat. Acad. Sci., I., 1. — Id., '99. The Chromoplasts and the Chromioles: B. C, XIX., 4. — Eismond, J., '95. Einige Beitrage zur Kenntniss der Attraktionsspharen und der Centrosomen: A. A., X. — Endres and "Walter, '95. Anstichversuche an Eiern von Rana fusca : A. Entwm.^ II., 1 . — Engelmann. T. W., '80. Zur Anatomie und Physiologie der Flimmerzellen : Arch. ges. Phys., XXIII. — von Erlanger, R., '96, 1. — Die neuesten Ansichten liber die Zelltheilung und ihre Mechanik: Zoo/. Centralb., III., 2. — Id., '96, 2. Zur Befruchtung des Ascariseies nebst Bemerkungen iiber die Struktur des Protoplasmas und des Centrosomas: Z. A., XIX. — Id., '96, 3. Neuere Ansichten iiber die Struktur des Protoplasmas: Zoo/. Centralb., III., 8,9. — Id., '96, 4. Zur Kenntniss des feineren Baues des Regenwurmhodens, etc. : A. m. A., XLVII. — Id., '96, 5. Die Versonische Zelle : Zo'dl. Centralb., III., 3. — Id., '96, 6. Die Entwicklung der mannlichen Geschechtszellen : Ibid., III., 12. — Id., '97, 1. tlber Spindelreste und den echten Nebenkern, etc.: Zo'dl. Centralb., IV., 1. — Id., '97, 2. Uber die sogenannte Sphare in den mannlichen Geschlechtszellen : Ibid., IV., 5. — Id., '97, 3. t*ber die Chromatinreduktion in der Entwicklung der mannlichen Geschlechtszellen : Ibid., IV., 8. — Id., '97, 4. Beitrage zur Kenntniss des Protoplasmas, etc. A. m. A., XLIX. — Id., '97,5. tU)er die Spindelbildung in den Zellen der Cephalopoden Keimscheibe : /?. C, XVII., 20. — Id., '98. Tber die Befruchtung, etc., des Seeigeleies : B. C, XVIII., 1. — Errera, *86. Eine fundamentale Gleichgewichtsbedingung organischen Zellen: Ber. Deutsch. Bot. Ges., 1886. — Id., '87. Zellformen und Seifenblasen : TagcbL der 60 Versammlung deutschcr Naturforscher und AerzU zu Wiesbaden, 1887.

FAIRCHILD, D. O., '97. t'ber Kerntheilung und Befruchtung bei Basidiobolus : Jahrb. wiss. Bot.. XXX. — Farmer, J. B., '93. On nuclear division of the pollen-mother-cell of Lilium Martagon : Ann. Bot. VII., 27. — Id.. '94. Studies in Hepaticae: Ibid., VIII., 29. —Id., '95, 1. Uber Kernteilung in Lilium-Antheren, besonders in Bezug auf die Centrosomenfrage : Flora, 1895, p. 57. — Id., 95, 2. On Spore-formation and Nuclear Division in the Hepaticae: Ann. Bot., IX. — Farmer and Moore, '95. On the essential similarities existing between the heterotype nuclear divisions in animals and plants: A. A., XI., 3. — Farmer and Williams, '96. On Fertilization, etc., in Fucus : Ann. Bot., X. — Pick, R., '93. t*ber die Reining und Befruchtung des Axolotleies : Z.w.Z., LVI., 4. — Id., '97. Bemerkungen zu M. Heidenhain's Spannungsgesetz : Arch. Anat. //. Phys. (Anat.). — Fiedler, C, '91. Entwickelungsmechanische Studien an Echinodermeneiern : Festschr. Nagcli u. Kolliker. Zurich, 1891. — Field, O. W., '95. On the Morphology and Physiology of the Echinoderm Spermatozoon: /. J/., XI. — Fischer, A., '94, 1. Zur Kritik der Fixierungsmethoden der Granula: A. A., IX., 22.—


Id., 94, 2. — t'ber die Geisseln einiger Flagellaten: /. w. B. XXVII. — Id., '95. Neue Beitrage zur Kritik der Fixierungsmethoden : A. A., X. — Id., '97. Untersuchungen iiber den Bau der Cyanophyceen und Bakterien : Jena* Fischer. — Id., '99. Fixierung, Farbung und Bau des Protoplasmas : Ibid. — Flemming, W., '75. Studien in der Entwicklungsgeschichte der Najaden: Sitzb. d. k. k. Akad. IViss. IVien, LXXI., 3. — Id., '79,1. Beitrage zur Kenntniss der Zelle und ih re Lebenserscheinungen, I. : A. m. A., XVI. — Id., '79, 2. Uber das Verhalten des Kerns bei der Zelltheilung, etc.: Virchow's Arch., LXXVII. — Id.. '80. Beitrage zur Kenntniss der Zelle und ihrer Lebenserscheinungen, II. : A. m. A., XIX. — Id., '81. Beitrage zur Kenntniss der Zelle und ihrer Lebenserscheinungen, III. : Ibid., XX.— Id., '82. Zellsubstanz, Kern und Zellteilung: Leipzig, 1882. — Id., '87. Neue Beitrage zur Kenntniss -der Zelle: A. m. A., XXIX. — Id., '88. Weitere Beobachtungen iiber die Entwickelung der Sperm atosomen bei Salamandra maculosa : Ibid., XXXI. — Id., '91-'97. Zelle, I.-VI. : Ergebn. Anat. u. Entwicklungsgesch. {Merkel and Bonnet), 1891-97. — Id., '91,1. Attraktionsspharen u. Centralkorper in Gewebs- u. Wanderzellen : A. A. — Id., '91, 22. Neue Beitrage zur Kenntniss der Zelle, II. Teil: A. m. A., XXXVII.— Id., '95, 1. Uber die Struktur der Spinaiganglienzellen : Verhandl. der anat. Gesellschaft in Basel, 17 April, 1895, p. 19. — Id., '95, 2. Zur Mechanik der Zelltheilung -.A.m. A., XLVI. — Id., '97, 2. Ueber den Bau der Bindegewebszellen, etc.: Zeit. Biol., XXXIV '. — Floderus, M., '96. tJber die Bildung der Follikelhullen bei den Ascidien : Z. w. Z., LXI., 2. — Pol, H., '73. Die erste Entwickelung des Geryonideies : /. Z., VII. — Id., '75. Etudes sur le deVeloppement des Mollusques. — Id., '77. Sur le commencement de Thdnogenie chez divers animaux : Arch. Sci. Nat. et Phys. Geneve, LVIII. See also Arch. Zool. Exp., VI. — Id., '79. Recherches sur la fecondation et la commencement de The'nogenie: Mbn. de la Soc. de physique et d^hist. nat., Geneve. XXVI. — Id., '91. Le Quadrille des Centres. Un episode nouveau dans Thistoire de la fe'condation : Arch, des sci. phys. et nat., 15 Avril, 1891 ; also, A. A., 9-10. 1891. — Foot, K., '94. Preliminary Note on the Maturation and Fertilization of Allolobophora : J. M., IX., 3, '94. — Id., '96. Yolk-nucleus and Polar Rings: Ibid., XII., 1. — Id., '97. The Origin of the Cleavage Centrosomes: /. M., XII., 3. — Francotte, P., '97. Recherches sur la maturation, etc., chez les Polyclades : Mem. cour. Acad. Sci. Belg.

— Frenzel, J., '93. Die Mitteldarmdruse des Flusskrebses und die amitotische Zelltheilung: A. m. A., XLI. — Fromman, C, '65. t)ber die Struktur der Bindesubstanzzellen des RUckenmarks: Centrl. f. med. Wiss., III., 6. — Id., '75. Zur Lehre von der Structur der Zellen: /. Z., IX. (earlier papers cited). — Id., '84. Untersuchungen iiber Struktur, Lebenserscheinungen und Reactionen thierischer und pflanzlicher Zellen: J.Z., XVII. — Fiirst, E., '98. Uber Centrosomen bei Ascaris: A. m. A., LII. — Fulmer, E. L., '98. Cell-division in Pine Seedlings: Bet. Gaz., XXVI., 4.

GAIiEOTTI, GINO, '93. t!ber experimentelle Erzeugung von Unregelmassigkeiten des karyokinetischen Processes: Bei. zur patholog. Anat. u. z. Altg. Pathol., XIV '.,2, Jena, Fischer, 1893. — Gallardo, Angel, '96. La Carioquinesis : Ann. Soc. Cientif. Argentina, XLII. — Id., '97. Significado Dinaraico de las Figuras Cariocineticas : Ibid., XLIV. — Gardiner, E. G., '98. The Growth of the Ovum, etc., in Polvchoerus: /. M., XV., 1. — Gardiner, W., '83. Continuity of Protoplasm in Vegetable Cells: Phil. Trans., CLXXIV. — Garnault, '88, '89. Sur les phe'nomenes de la fe'condation chez Helix aspera et Arion empiricorum : Zool. Anz., XI., XII. — Geddes and Thompson. The Evolution of Sex: London, 1899. —

— Gegenbaur, C, '54. Beitrage zur naheren Kenntniss der Schwimmpolypen : Z. w. Z., V. — Van Gehuchten, A., '90. Recherches histologiques sur Tappareil digestif de la larve de la Ptychoptera contaminata : La Cellule, VI. — Giard, A., '77.


Sur la signification morphologique des globules polaires : Revue scientifiqut, XX. — Id., '90. Sur les globules polaires et les homologues de ces e'le'ments chez les infusoires cilids : Bulletin scientifique de la France et de la Belgique, XXII. — Godlewsky, E., '97, 1. t v ber mehrfache bipolar Mitose bei der Spermatogenese von Helix: Anz. Akad. Wiss. Krakau. — Id., '97, 2. Weitere Untersuchungen iiber die Umwandlung der Spermatiden, etc. : Am. Akad. Wiss. Krakau., Nov., "97.

— Goroschanktin, J., '83. Zur Kenntniss der Corpuscula bei den Gymnospermen : Bot. Zeit., LXI. — Graf, A., '97. The Individuality of the Cell : N. Y. State Hosp. Bull., April. — Gr6goire, V., "99. Les cineses polliniques dans les LiJiacees: Bot. Centb., XX., 1 ; La Cellule. XVI., 2. — Griffin, B. B., , 96. The History of the Achromatic Structures in the Maturation and Fertilization of Thalassema : Trans. N. Y. Acad. Set. — Id., '99. Studies on the Maturation, Fertilization, and Cleavage of Thalassema and Zirphaea : /. AI., XV. — Gierke, H., -85. Farberei zu mikroskopischen Zwecken : Zeit. Wiss. Alik., II. — Grobben, C, '78. Beitrage zur Kenntniss der mannlichen Geschlechtsorgane der Dekapoden : Arb. Zool. Inst. Witn* I.

— Gruber, A., '84. tJber Kern und Kerntheilung bei den Protozoen : Z. w. Z~> XL. — Id., '85. liber kiinstliche Teilung bei Infusorien: B. C, IV., 23; V., 5.— Id., '86. Beitrage zur Kenntniss der Physiologie und Biologie der Protozoen : Ber. Naturf. Ges. Freiburg,!. — Id., '93. Mikroscopische Vivisektion : Ber. d. IVafnrf. Ges. zu Freiburg, VII., 1. — Id., *97. Weitere Beobachtungen an vielkernigen Infusorien : Ber. Naturf. Ges. Freiburg, III. — Guignard, L., '89. De'veloppement et constitution des Antherozoides : Rev. gen. Bot., I. — Id., '91, 1. Nouvelles eludes sur la fe'eondation : Ann. d. Sciences Nat. Bot., XIV. — Id., '91, 2. Sur Texistence des '* spheres attractives" dans les cellules ve'ge'tales: C.R., 9 Mars. — Id., ^98, 1. Les centres antiques chez les ve*ge*taux : Ann. Sci. Nat. Bot., (VIII.) V. ; also, Bot. Gaz., XXV. — Id., '98, 2. Le developpement du pollen et la reduction chromatique dans le Nat's major : Arch. Anat. Mik., II., 4. — Id., '99. Sur les antherozoides et la double copulation sexuelle chez les ve'ge'taux angiospermes : C. R., CXXVIII., 14.

HABERLANDT, G.. '87. tJber die Beziehungen zwischen Funktion und Lage des Zellkerns: Fischer, 1887. — Hackel, E., '66. Generelle Morphologie. — Id.. '91. Anthropogenic 4th ed.. Leipzig, 1891. — Hacker, V., 92, 1. Die Furchung des Eies von /Equorea Forskalea: A. tn. A., XL. — Id., "92, 2. Die Eibildung bei Cyclops unci Canthocamptus : Zool. fahrb., V. — Id., '92, 3. Die heterotypische Kerntheilung im Cyclus der generativen Zellen : Ber. naturf. Ges. Freiburg. VI. — Id, '93. Das Keimblaschen, seine Elemente und Lageveranderungen : A. tn. A.. XLI. — Id.. '94. t*ber den heutigen Stand der Centrosomenfrage : Verhandl. d. deutschen Zool. Ges.. 1894, p. 11. — Id.. *95. 1. Die Vorstadien der Eireifung: A. t/t. A., XLV., 2. — Id., '95, 2. Zur frage nach dem Vorkommen der Schein-Reduktion bei den Pflanzen : Ibid., XLVI. Also Ann. Bot., IX. — Id., '95, 3. Uber die Selbstandigkeit der vaterlichen und miitterlichen Kernsbestandtheile wahrend der Embryonalentwicklung von Cyclops: A. m. A., XLVI.. 4.

— Id., '97,1. Die Keimbahn von Cyclops : A. tn. A., XLIX. — Id., "97, 2. Tber weitere t^bereinstimmungen zwischen den Fortpflanzungsvorgangen der Thiere und Pflanzen : B. C, XVII. — Id., "98. t v ber vorbereitende Theilungsvorgange bei Thieren und Pflanzen: Verh. d. Zool. Ges., VIII. — Id.. '99. Praxis und Theorie der Zellen und Befruchtungslehre : fena, Fischer. — Hallez. P.. *86. Sur la loi de l'orientation de l'embryon chez les insectes : C. R., 103. 1886. — Halliburton, W. D.. '91. A Text-book of Chemical Physiology and Pathology: London.

— Id.. '93. The Chemical Physiology of the Cell: (Gouldstonian Lectures) Brit. Aled. fount. — Hammar, J. A., '96. Cber einen primaren Zusammenhang zwischen den Furchungszellen des Seeigeleies : A. tn. A.. XLVII., 1. — Id.. '97. t*ber einc allgemein vorkommende primare Protoplasmaverbindung zwischen den Bias


tomeren: A. m. A., XL1X. — Hammarsten, O., ^4. Zur Kenntniss der Nucleoproteiden: Zeit. Phys. Chem., XIX. — Id., '95. Lehrbuch der physiologischen Chemie, 3e Ausgabe : Wiesbaden, 1895. — Hansemann, D., '91. Karyokinese und Cellularpathologie : Berl. Klin. Wochenschrift, No. 42. — Id., '93. Spezificitat, Altruismus und die Anaplasie der Zellen: Berlin, 1893. — Hanstein, J., ? 80. Das Protoplasma als Trager der pflanzlichen und thierischen Lebensverrichtungen. Heidelberg. — Harper, R. A., , 96. Cber das Verhalten der Kerne bei der Fruchtentwickelung einiger Ascomyceten: Jahrb. wiss. Bot., XXIX. — Id., '97. Kernteilung und freie Zellbildung im Ascus: Ibid., XXX. — Hardy, W. B., '99. On the Structure of Cell-protoplasm: Jour. Phys.. XXIV., 2. — Harvey, Wm., 1651. Exercitationes de Generatione Animalium : London. Trans, in Sydenham Soc, X., 1847. — Hartog, M. M., '91. Some Problems of Reproduction, etc. : Q.J., XXXIII. — Id., '96. The Cytology of Saprolegnia: Ann. Bot., IX. — Id., '98. Nuclear Reduction and the Function of Chromatin: Nat. Sci., XII. — Hatschek, B., '87. Cber die Bedeutung der geschlechtlichen Fortpflanzung: Prager Med. Wochenschrift, XLVI. — Id., , 88. Lehrbuch der Zoologie.— Heath, H., '99. The Development of Ischnochiton : Jena, Fischer. — Heidenhain, M., ^93. liber Kern und Protoplasma : Festchr. z. jo-Jdhr. Doctorjub. von v. Kolliker : Leipzig. — Id., , 94. Neue Untersuchungen liber die Centralkorper und ihre Beziehungen zum Kern und Zellenprotoplasma : A. m. A.,XLlll. — Id., '95. Cytomechanische Studien : A. Entwm., I., 4. — Id., '96, 1. Ein neues Modell zum Spannungsgesetz der centrirten Systeme : Verh. anat. Gcs. — Id., '96, 2. Uber die Mikrocentren mehrkerniger Ricsenzellen, etc. : Morph. Arb., VII., 1. — Id., '99. Uber eine eigenthtimliche Art Knospung an Epithelzellen, etc. : A. m. A., LIV., 1. — Heidenhain and Conn,' 97. Uber die Mikrocentren in den Geweben des Vogelembryos, etc.: Morph. Arb., VII. — Heitzmann, J., '73. Untersuchungen liber das Protoplasma : Sits. d. k. Acad. Wiss. Wien., LXVII. — Id., '83. Mikroscopische Morphologie des Thierkorpers im gesunden und kranken Zustande : Wien, 1883. — Henking, H. Untersuchungen Uber die ersten Entvvicklungsvorgange in den Eiern der Insekten, I., II., III.: Z. w. Z., XLIX., LI., LIV., 1890-92. — Henle, J., '41. Allgemeine Anatomie: Leipzig. — Henneguy, L. P., '91. Nouvelles recherches sur la division cellulaire indirecte: Joum. Anat. et Physiol., XXVII. — Id., 93. Le Corps vitellin de Balbiani dans Toeuf des Ve'rte'bres : Ibid., XXIX. — Id., ^96. Lecons sur la cellule: Paris. — Id., '98. Sur les rapports des cils vibratils avec les cgntrosomes : Arch. Anat. Mik., 1. — Hensen, V., '81. Physiologic der Zeugung : Hermann's Physiologie, VI. — Herbst, C. Experimented Untersuchungen uber den Einfluss der veranderten chemischen Zusammensetzung des umgebenden Mediums auf die Entwicklung der Thiere, I. ; Z.w. Z., LV., 1892 ; lh,Mitt. Zool. St. Neapet,Xh, 1893; Ul.-Vl., Arch. Entwm., II., 4, 1896. — Id., '94, '95. Uber die Bedeutung der Reizphysiologie fiir die Kausale AufFassung von Vorgangen in der tierischen Ontogenese: Biol. Centralb., XIV., XV., 1894, 1895. — Herla, V., '93. Etude des variations de la mitose chez Tascaride me'galoce'phale : A. B., XIII. — Herlitzka, A., '95. Contributo alio studio della capacita evolutiva dei due primi blastomeri neir uove di Tritone: A. Entwm., II., 3. — Hermann. F., '89. Beitrage zur Histologic des Hodens : A. m. A.. XXXIV. — Id., '91. Beitrag zur Lehre von der Entstehung der karyokinetischen Spindel: Ibid., XXXVII. — Id., "92. Urogenitalsystem, Struktur und Histiogenese der Spermatozoen : Merkel und Bonnet's Ergebnisse, II. — Id., '97. Beitrage zur Kenntniss der Spermatogenese: A. m. A., L. — Hertwig, O., '75. Beitrage zur Kenntniss der Bildung, Befruchtung und Teilung des tierischen Eies, I. : M. J., I. — Id., -77. Beitrage, etc., II. ; Ibid., III. — Id., '78. Beitrage, etc.. III. ; Ibid., IV. — Id., '84. Das Problem der Befruchtung und der Isotropic des Eies, eine Theorie der Vererbung : /. Z., XVIII. — Id., '90, 1. Vergleich der Ei- und Samenbildung bei Nematoden. Eine


Grundlage fur cellulare Streitfragen : A. m. A., XXXVI. — Id., "90, 2. Experimentelle Studien am tierischen Ei vor, wahrend und nach der Befruchtung : /. Z., 1890. — Id., '92, 1. — Urmund und Spina Bifida: A, m. A., XXXIX. — Id., 92,2. Aeltere und neuere Entwicklungs-theorieen : Berlin. — Id., '93, 1. Uber den Werth der ersten Furchungszellen fiir die Organbildung des Embryo : A. m, A^ XLII.— Id., 93, 2. Die Zelle und die Gewebe: Fischer, Jena, 1893, 1898.— Id., '94. Zeit und Streitfragen der Biologie: Berlin. — Hertwig, O. and R., "86. Experimentelle Untersuchungen Uber die Bedingungen der Bastard befruchtung : /. Z., X IX . — Id., '87. tlber den Befruchtungs- und Teilungsvorgang des tierischen Eies unter dem Einfluss ausserer Agentien : Ibid., XX. — Hertwig, R., "77. Uber den Bau und die Entwicklung der Spirochona gemmipara: Ibid.* XI. — Id.. "84. Die Kerntheilung bei Actinosphaerium Eichhorni : Ibid., XVII. — Id., '88. Uber Kernstruktur und ihre Bedeutung fiir Zellteilung und Befruchtung: Ibid., IV., 1888.

— Id., '89. Uber die Konjugation der Infusorien: Abh. der bayr. Akad. d. Hiss., II., CI., XVII. — Id., '92. Uber Befruchtung und Conjugation : Verh. deutsch. Zool. Ges., Berlin. — Id., "95. Uber Centrosoma und Centralspindel : Silz.-Ber. Ges. Morph. und Phys., Miinchen, 1805, Heft I. —Id., '96. Uber die Entwicklung des unbefruchteten Seeigeleies, etc. : Festchr. f. Gegenbaur. — Id., *97, 1. tJber die Bedeutung derNucleolen : Silzb. Ges. Morph. Phys. Miinchen, 1898, I. — Id., *97, 2.

— Uber Karyokinese bei Actinosphaerium : Silzb. Ges. Morph. Phys. Miinchen, XIII.,

1. — Id., '98. Kerntheilung, Richtungskorperbildung und Befruchtung von Actinosphaerium: Abh. A", bayer. Akad. Wiss., XIX, 2. — Heuser, E., 84. Beobachtung uber Zelltheilung : Bol. Cent. — Hill, M. D., '95. Notes on the Fecundation of the Egg of Sphcerechinus granularis and on the Maturation and Fertilization of the Egg of Phallusia mammillala: Q. /., XXXVIII. — Hirase, S., 37. Untersuchungen liber das erhalten des Pollens von Gingko biloba : Bol. Centb., LXIX.,

2, 3. — Id., '98. fitudes sur la fe*condation et rembryogc"nie der Gingko: Jour. Coll. Sci., Tokio, XII. — His. W.,'74. Unsere Korperform und das physiologische Problem ihrer Entstehung : Leipzig. — Hofer, B., -89. Experimentelle Untersuchungen iiber den Einfluss des Kerns auf das Protoplasma: J. Z., XXIV. — Hoffman, R. W., '98. Uber Zellplatten und Zellplattenrudimente : Z. w. Z.. LXIII.

— Hofmeister. '67. Die Lehre von der Pflanzenzelle : Leipzig, 1867. — Holl, M.. '90. Uber die Reifung der Eizelle des Huhns : Silzb. Acad. Wiss. H'ien. XCIX., 3. — Hooke, Robt., 1665. Mikrographia, or some physiological Descriptions of minute Bodies by magnifying Glasses: London. — Hoyer. H.. *90. t*ber ein fiir das Studium der " direkten v Zelltheilung vorzliglich geeignetes Objekt : A. A., V. — Hubbard, J. W., '94. The Yolk-Nucleus in Cymatogaster : Proc. Am. Phil. Soc, XXXIII. — Huie. L.. '97. Changes in the Cell-organs of Drosera produced by Feeding with Egg-albumen: Q. J., XXXIX. — Humphrey, J. B., '94. Nucleolen und Centrosomen : Per. deutschen bot. Ges., XII., 5. — Id.. "95. On some Constituents of the Cell: Attn. Bot.. IX. — Huxley. T. H., '53. Re\iew of the Cell-theory: Brit, and Foreign Med.-Chir. Review, XII. — Id., '78. Evolution in Biology, Enc. Brit., 9th ed., 1878; Science and Culture, N. Y., 1882.

IKENO, S., '97. Vorlaufige Mitth. uber die Spermatozoiden bei Cycas: Bot. Ccntb., LXIX., 1. — Id., '98, 1. Zur Kenntniss des sogenannten centrosomahnlichen Korpers im Pollenschlauche der Cycaden : Flora, LXXXV., 1. — Id., '98, 2. Untersuchungen iiber die Entwickelung der Geschlechtsorgane, etc., bei Cycas : Jahrb. wiss. Bot.. XXXII., 4. — Ishikawa, M., '91. Vorlaufige Mitteilungen Uber die Konjugationserscheinungen bei den Noctiluceen : Z. A., No. 353, 1891. — Id., '94. Studies on Reproductive Elements: II., Noctiluca miliar is Sur., Its Division and Spore-formation: Journ. College of Sc. Imp. Univ. Japan, VI. — Id., *97. Die


Entwickelung der Pollenkorner von Allium: Journ. Coll. Sci. Tokyo, X., 2. — Id.,

  • 99. Further Observations on the Nuclear Division of Noctiluca : Ibid., XII., 4.

JENNINGS, H. S., '96. The Early Development of Asplanchna: Bull. Mus. Comp. Zool., XXX. — Jensen, O. S., '83. Recherches sur la spermatoge'nese : A. B., IV. — Johnson, H. P., '92. Amitosis in the embryonal envelopes of the Scorpion: Bull. Mus. Comp. Zool., XXII., 3. — Jordan, E. O., '93. The Habits and Development of the Newt: /. M., VIII., 2. — Jordan and Eycleshymer, '94. On the Cleavage of Amphibian Ova: /. A/., IX., 3, 1894. — Juel, H. O., '97. Die Kerntheilungen in den Pollenmutterzellen, etc. : Jahrb. wiss. Bot., XXX. — Julin, J., "93, 1. Structure et developpement des glandes sexuelles, ovogdnese, spermatoge'nese et fe'eondation chez Styleopsis grossularia : Bull. Sc. de France et de Belgique, XXIV. — Id., '93, 2. Le corps vitellin de Balbiani et les eUe'ments des Me'tazoaires qui correspondent au Macronucle\is des Infusoires cilie's: Ibid., XXIV.

KARSTEN, G, 96. Untersuchungen tiber Diatomeen : Flora, LXXXIL — Keuten, J., ^5. Die Kerntheilung von Euqlena viridis Ehr: Z.w.Z., LX. — Kienitz-Gerloff, P., '91. Review and Bibliography of Researches on Protoplasmic Connection between adjacent Cells: in Bot. Zeitung, XLIX. — Kingsbury, B. P.,

  • 99. The Reducing Divisions in the Spermatogenesis of Desmognathus : Zool.

Bull.. II., 5. — Klebahn, '90. Die Keimung von Closterium und Cosmarium : Jahrb. wiss. Bot., XXII. — Id., '92. Die Befruchtung von CEdigonium : Jahrb. f. wiss. Bot., XXIV. — Id., '96. Beitrage zur Kenntniss der Auxosporenbildung, I., Rhopalodia : JaJtrb. wiss. Bot., XXIX. — Klebs, G., '83. Uber die Organisation einiger Flagellaten-Gruppen, etc. : Bot. Inst. Tubingen, I., 1. — Id., '04. Uber die neueren Forschungen betreffs der Protoplasmaverbindungen benachbarter Zellen : Bot. Zeit., 188.4 — Id., '87. Uber den Einfluss des Kerns in der Zelle: B. C, VII. — Klein, E., , 78- , 79. Observations on the Structure of Cells and Nuclei : Q. J., XVIII., XIX.

— Klinckowstr&m, A. v., '97. Beitrage zur Kenntniss der Eireife und Befruchtung bei Prostheceraeus : A. m. A., XLVIII. — von K&lliker, A., '41. Beitrage zur Kenntniss der Geschlechtsverhaltnisse und der Samenflussigkeit wirbelloser Tiere : Berlin. — Id., '44. Entwicklungsgeschichte der Cephalopoden : Zurich. — Id., '85. Die Bedeutung der Zellkerne fur die Vorgange der Vererbung: Z. w. Z., XLII. — Id., '86. Das Karyoplasma und die Vererbung, eine Kritik der Weismann'schen Theorie von der Kontinuitat des Keimplasmas : Ibid., XLIII. — Id., '89. Handbuch der Gewebelehre, 6th ed. : Leipzig. — Id., 97. Die Energiden von Sachs, etc.: Verh. Phys. Med. Ges., Wurzburg, XXXI., 5. — Korff, 39. Zur Histogenese der Spermien von Helix : A. m. A., LIV. Korschelt, E., '89. Beitrage zur Morphologie und Physiologie des Zell-kernes: Zool. Jahrb. Anat. u. Ontog., IV. — Id., ^3. Uber Ophryotrocha puerilis: Z. w. Z., LIV. — Id., '95. Uber Kerntheilung, Eireifung und Befruchtung bei Ophryotrocha puerilis : Ibid., LX. — Id., '96. Kernstructuren und Zellmembranen in den Spinndrusen der Raupen: A. m. A., XLVII.

— Id., 37. Uber den Bau der Kerne in den Spinndrusen der Raupen : Ibid., XLIX.

— Kossel, A., '91. Uber die chemische Zusammensetzung der Zelle : Arch. Anat. u , Phys. — Id., 33. Uber die Nucleinsaure : Ibid., 1893. —Id., '96. Uber die basischen Stoffe des Zellkernes : Zeit. Phys. Chem., XXII. — von Kostanecki, K., 31 . Uber Centralspindelkorperchen bei karyokinetischer Zellteilung : Anat. Hefte, 1892. dat. 91. — Id., "96. Uber die Gestalt der Centrosomen im befruchteten Seeigelei: Ibid,, VII., 2. — Id., '97, 1. Uber die Bedeutung der Polstrahlung, etc. : A. m. A., LXIX. — Id., '98. Die Befruchtung des Eies von Myzostoma : Ibid., LI. — Kostanecki and Siedlecki, 96. Uber das Verhalten der Centrosomen zum Protoplasma: Ibid., XLIX. — Kostanecki and Wierzejski, 1 96. Uber das Verhalten der sogenannten achromatischen Substanzen im befruchteten Ei : Ibid., XLII., 2. — Ktthne, W., '64. Untersuchungen Uber das Protoplasma und die Con


tractilitat. — Kupffer, C, '75. tfber Differenzierung des Protoplasma an den Zellen thierischer Gewebe: Schr. natur. Ver. Schles.-Holst '.* I., 3. — Id., '90. Die Entwicklung von Petromyzon Planeri: A. m. A., XXXV. — Id., *96. tTber Energiden und paraplastische Bildungen : Rek/oratrede* Munchen* 1896.

LAMEERE, A., *90. Recherches sur la reduction karyogamique : BruxelUs. — Lauterborn, R., '93. Uber Bau und Kerntheilung der Diatomeen : Verh. d. Natur h. Med. Ver. in Heidelberg* 1893. — Id., '95. Protozoenstudien, Kern- und Zellteilung von Ceratium hirundinella O. F. M. : Z. w. Z.* XLIX. — Id., *96. — La Valette St. George, '65. tlber die Genese x der Samenkdrper : A. m. A.* 1.— Id., '67. t)ber die Genese der Samenkorper, II. (Terminology): Ibid.* III.— Id., '76. Die Spermatogenese bei den Amphibien: Ibid.* XII. — Id., ^78. Die Spermatogenese bei den Saugethieren und dem Menschen : Ibid., XV. — Id., , 85-*87. Spermatologische Beitrage, I.-V.: Ibid, XXV., XXVII., XXVIIL, and XXX.

— Lankester, E. Ray, '77. Notes on Embryology and Classification : London.— Lavdovsky, M., 1 94. Von der Entstehung der chromatischen und achromatischen Substanzen in den tierischen und pnanzlichen Zellen : Merkel und Bonnets Anal. Hef/e* IV., 13. — Lawson, A. A., '98. Some Observations on the Development of the Karyokinetic Spindle, etc. : Proc. Cat. Acad. Sci., I., 5. — Lazarus, A., *S8. Die Anaemie: Wien. — Lee, A. Bolles, , 96. Sur le Nebenkern, etc., chez Helix: La Cellule* XI. — Id., '97. Les cineses spermatoge'ne'tiques chez Helix: Ibid., XIII. — von LenhoBse'k, M., 95. Centrosom und Sphare in den Spinalganglien des Frosches: A. m. A., XLVI. — Id., '98, 1. Uber Flimmerzellen : Verh. An. Ges.* XII. — Id., '98, 2. Untersuchungen Uber Spermatogenesis: A. m. A., LI. — Id., '99. Das Mikrocentrum der glatten Muskelzellen : A. A., XVI., 13, 14. — Ley dig, Pr., '54. Lehrbuch der Histologic des Menschen und der Thiere : Frankfurt. — Id., '85. Zelle und Gewebe, Bonn. — Id., '89. Beitrage zur Kenntniss des thierischen Eies im unbefruchteten Zustande : SpengeVsJahrb. A not. On/.. III.

— Lilienfeld, L., '92, ^93. Uber die Verwandtschaft der Zellelemente zu gewissen Farbstoflfen: ' Verh. Phys. Ges., Berlin, 1892-93. —Id., '93. Uber die Wahlverwandtschaft der Zellelemente zu Farbstoflfen : A. A. P.* 1893. — Lillie, P. R.. '95. The Embryology of the Unionidae : /. J/., X. — Id.,. '96. On the Smallest Parts of Stentor capable of Regeneration : /. M.* XII., 1. — Id., '97. On the Origin of the Centres of the First Cleavage-spindle in Unio: Science, V. — Id., *98. Centrosome and Sphere in the Egg of Unio: Zool. Bull.. I.. 6. — Id., '99. Adaptation in Cleavage : Wood's Moll Biol. Led. — List, Th., '96. Beitrage zur Chemie der Zelle und Gewebe, I. : Mitth. Zool. St. Neap.* XII., 3. — Loeb, J., '91-'92. Untersuchungen zur physiologischen Morphologic I. Heteromorphosis : HUrzburg. 180J. II. Organbildung und Wachsthum : Ibid.* 1892. — Id., '92. Experiments on Cleavage : J. M.* VII. — Id., '93. Some Facts and Principles of Physiological Morphology: Wood's H oil Biol. Lectures* 1893. — Id., "94. Uber die Grenzen der Theilbarkeit der Eisubstanz : A. %cs. P.* LIX., 6, 7. — Id., ^5. Cber Kerntheilung ohne Zelltheilung : Arch. Entwm.. II. — Id., "99, 1. Warum istdie Regeneration kernloser Protoplasmastiicken unmoglich, etc.: Ibid.* VIII., 4. — Id., "99. 2. On the Nature of the Process of Fertilization and the Artificial Production of Normal Larv;t\ etc. : Am. Journ. Phys.. III., 3. — Ldwit, M., '91. Uber amitotische Kerntheilung: B. CXI. — Lukjanow, '91. Grundzuge einer allgemeinen Pathologic der Zelle: Leipzig. — Lustig and Galeotti, *93. Cytologische Studien uber pathologische menschliche Gewebe : Bcitr. Path. Ana/.* XIV.

MACALLUM. A. B., '91. Contribution to the Morphology and Physiology of the Cell: Trans. Canad. Inst.. I., 2.— McClung, C. E., '99. A Peculiar Nuclear Element in the Male Reproductive Cells of Insects: Zool. Bull.* II., 4. — MacFar


land. F. M., '97. Cellulare Studien an Molluskeneiern : Zool.Jahrb. Anat., X. — McGregor, J. H., '99. The Spermatogenesis of Amphiuma: /. Af., XV., Suppl. — McMurrich, J. P., '86. A Contribution to the Embryology of the Prosobranch Gasteropods: Studies Biol. I jab. Johns Hopkins Univ., III. — Id., '95. Embryology of the Isopod Crustacea: /. Af., XL, 1. — Id., '96. The Yolk-Lobe and the Centrosome of Fulgur : A. A., XII., 23. —Id., '97. The Epithelium of the Midgut of the Terrestrial Isopods: /. Af., XIV., 1. — Maggi, L., '78. I plastiduli nei ciliati ed i plastiduli liberamente viventi: Atti. Soc. Ital. Sc. Nat. Afilano, XXI. (also later papers). — Malfatti, H., *91. Beitrage zur Kenntniss der Nucleine: Zeit. Phys. Chem., XVI. — Mark, E. L., *81. Maturation, Fecundation, and Segmentation of Limax campestris: Bull. Afus. Cotnp. Zool. Harvard College* VI. — Mathews, A. P., '97, 1. Internal Secretions considered in Relation to Variation and Development: Science, V., 122. — Id., '97, 2. Zur Chemie der Spermatozoen : Zeit. Phys. Chem., XX ML, 4, 5. — Id., '98. A Contribution to the Chemistry of Cytological Staining: Am.Journ. Phys., I., 4. — Id., '99, 1. The Origin of Fibrinogen: Ibid., III. — Id., '99,2. The Metabolism of the Pancreas Cell: /. J/., XV., Suppl. — Maupas, M., '88. Recherches expe'rimentales sur la multiplication des Infusoires cilie's: Arch. Zool. Exp., 2me sdrie, VI. — Id., '89. Le rejeunissement karyogamique chez les Cilie's: /bid., 2me se*rie, VII. — Id., '91. Sur le de'terminisme de la sexuality chez THydatina senta: C. R., Paris. — Mayer, P., ^l. Uber das Farben mit Carmin, Cochenille und Hamatein-Thonerde: Afitth. Zool. St. Neapol., X., 3. — Id., '97. Beruht die Farbung der Zellkerne auf einem chemischen Vorgang oder nicht?: A. A., XIII., 12. — Mead, A. D., ? 95. Some Observations on Maturation and Fecundation in Chaetopterus pergamentaceus Cuv. : /. A/., X., 1 . — Id., '97, 1. The Origin of the Egg-centrosomes : /bid., XII. — Id., '97, 2. The early Development of marine Annelids: /bid., V. — Id., ? 98, 1. The Origin and Behaviour of the Centrosomes in the Annelid Egg : /bid., XIV., 2. — Id., '98, 2. The Rate of Cell-division and the Function of the Centrosome: IVood's H oil Biol. Lectures. — Merkel, P., '71. Die Stiitzzellen des menschlichen Hodens: A/tiller's Arch. — Mertens, H., '93. Recherches sur la signification du corps vitellin de Balbiani dans Tovule des Mammiferes et des Oiseaux: A. B., XIII. — Metschnikoff, E., 66. Embryologische Studien an Insecten: Z.w.Z., XVI. — Meves, P., "91. t)ber amitotische Kernteilung in den Spermatogonien des Salamanders, und das Verhalten der Attraktionsspharen bei derselben: A. A., 1891, No. 22. — Id., "94. tfber eine Metamorphose der Attraktionssphare in den Spermatogonien von Salamandra maculosa: A. m. A., XLIV. — Id., '95. Uber die Zellen des Sesambeines der Achillessehne des Frosches (Rana temporaria) und iiber ihre Centralkbrper: /bid.,XLV. — Id., '96. Cber die Entwicklung der mannlichen Geschlechtszellen von Salamandra: /bid., XLVIII. — Id., '97, 1. Zur Struktur der Kerne in den Spinndrlisen der Raupen: /bid., XLVIII. — Id., '97, 2. Cber Struktur und Histiogenese der Samenfaden von Salamandra: /bid., L. — Id., '97, 3. Uber den Vorgang der Zelleinschnurung : Arch. Entwm., V '., 2. — Id., '97, 4. Zelltheilung : Merkel u. Bonnet, Erg., VI. — Id., ? 97, 5. tJber Centralkorper in mannlichen Geschlechtszellen von Schmetterlingen : A. A., XIV., 1. — Id., '98. ITber das Verhalten der Centralkorper bei der Histogenese der Samenfaden vom Mensch und Ratte: Verh. An. Ges., XIV. — Id., '99. tlber Struktur und Histogenesis der Samenfaden des Meerschweinschens : A. m. A., LIV. — Meyer, A., '96. Die Plasmaverbindungen, etc. : Bot. Zeit., 11, 12. — Meyer, O., ? 95. CellularUntersuchungen an Nematodeneiern : /. Z., XXIX. (XXIL). — Michaelis, L., '97. Die Befruchtung des Tritoneies: A. m. A., XLVIII. — Miescher, P., '96. Physiologisch-chemische Untersuchungen iiber die Lachsmilch : Arch. Exp. Path. u.Pharm.y XXXVII. — Mikosch, '94. Uber Struktur im pflanzlichen Protoplasma : Verhandl. d. Ges. deutscher Naturf. und Arste, 1 894 ; Abteil f. P/lanzen


physiologie u. Pflansenanatomie. — Minot, C. S., '77. Recent Investigations of Embryologists : Proc. Post. Soc. Nat. Hist., XIX. — Id., '79. Growth as a Function of Cells : Ibid., XX. — Id., '82. Theorie der Genotlasten : P. C, II., 12. See ako Am. Nat., February, 1880, and Proc. Post. Soc. Nat. Hist., XIX., 1877. — Id., ^1. Senescence and Rejuvenation : Journ. Phys.,Xl\., 2. — Id., , 92. Human Embryology. New York. — von Mohl Hugo, '46. Cber die Saftbewegung im Innern der Zellen : Pot. Zeitung. — Moll, J. W., '93. Observations on Karyokinesis in Spirogyra: Verh. Kon. Akad., Amsterdam, No. 9. — Montgomery, Th. H., "98, 1. The Spermatogenesis of Pentatoma, etc. : Zoo/. Jahrb. — Id., '98, 2. Comparative Cytological Studies, with Especial Reference to the Morphology of the Nucleolus : /. M., XV., 2. — Moore, J. E. S., '93. Mammalian Spermatogenesis: A. A., VIII. — Id., '95. On the Structural Changes in the Reproductive Cells during the Spermatogenesis of Elasmobranchs : Q. J , XXXVIII. — Morgan, T. H., '93. Experimental Studies on Echinoderm Eggs: A. A., IX., 5, 6. — Id., '95. 1. Studies of the " Partial " Larva of Sphaerechinus : A. Entwm., II., 1. — Id., '95, 2. Experimental Studies on Teleost-eggs : A. A., X., 19. — Id., '95, 3. Half-embryos and Whole-embryos from one of the first two Blastomeres of the Frog's Egg: Ibid., X., 19. — Id., '95, 4. The Fertilization of non-nucleated Fragments of Echinoderm-eggs : Arch. Entwm. , II., 2. — Id., ^95, 5. The Formation of the Fishembryo: J. M., X., 2. — Id., '96, 1. On the Production of artificial archoplasmic Centres: Rept. of the Am. Morph. Soc, Science, III., January 10, 1896. — Id., "96, 2. The Number of Cells in Larvae from Isolated Blastomeres of Amphioxus: Arch. Entwm., III., 2. — Id., '96,3. The Production of Artificial Astrosphaeres : Arch. Entwm. , III. — Id., '98, 1. Experimental Studies of the Regeneration of Planaria maculata: Ibid., VII., 2, 3. — Id., "98, 2. Regeneration and Liability to Injury: Zool. Pull., I., 6. — Id., '99, 1. The Action of Salt-solutions on the Unfertilized and Fertilized Eggs of Arbacia and other Animals : Arch. Entwm., VIII., 3. — Id., '99,2. A Confirmation of SpallanzanPs Discovery, etc.: A. A., XV. 21 . — Mottier, D. M., '97, 1. t'ber das Verhalten der Kerne bei der Entwicklung des Embryosacs, etc.: Jahrb. wiss. Pot., XXXI. — Id., '97, 2. Beitrage zur Kenntniss der Kerntheilung in den Pollenmutterzellen. *•/<:. : Ibid., XXX. — Id., '98. Das Centrosoma bei Dictyota : Per. D. Pot. Ges., XVI., 5. — Muller, E., '96. Uber die Regeneration der Augenlinse nach Exstirpation derselben bei Triton : A. m. A., XLVIL, 1.— Munson, J. P., '98. The Ovarian Egg of Limulus, etc.: J. J/., XV., 2. — Murray, J. A., '98. Contributions to a Knowledge of the Nebenkern in the Spermatogenesis of Pulmonata: Zool. Jahrb., XI., 14.

NADSON, G., '95. ttber den Bau des Cyanophyceen-Protoplastes : Script. Potan. Horti. PetropoL, IV. — Nageli, C, '84. Mechanisch-physiologische Theorie der Abstammungslehre : Munchen 11. Leipzig* 1884. — Nageli und Schwendeuer. ? 67. Das Mikroskop. (See later editions.) Leipzig. — Nawaachin, '99. Neue Beobachtungen uber Befruchtung bei Fritillaria und Lilium : Pot. Centb., LXXVIL, 2. — Nemec, B., '97. Tber die Stmktur der Diplopodeneier. A. A.. XIII., 10, n. — Id., '99. Uber die karvokinetischc Kerntheilung in den \Vurzelspitzen von Allium : J. w. P.. XX VIII, 2. — Newport, G. On the Impregnation of the Ovum in the Amphibia: Phil. Trans., 1851, 1853, 1854. — Norman. W. W.. "96. Segmentation of the Nucleus without Segmentation of the Protoplasm: Arch. Entwm., III. — Nussbaum, M., '80. Zur Differenzierung des Geschlcchts im Tierreich : A. m. A., XVIII. — Id., '84, 1. Uber Spontane und Kiinstliche Theilung von Infusorien : Verh. d. naturh. Ver. preus.. Rheinland, 1884. — Id., '84,2. Cber die Verandeningen der Geschlechtsproducte bis zur Eifurchung: A. m. A., XXIII. — Id., '85. Uber die Teilbarkeit der lebendigen Materie, I. : A. m. A., XXVI. —


Id., '94. Die mit der Entwickelung fortschreitende Differenzierung der Zellen : Sitz.-Ber. d. niederrhein. Gesellschaft f. Natur- u. Heilkunde, Bonn, 5 Nov., 1894; also/?. C, XVI., 2, 1896. — Id., ? 97. Die Entstehung des Geschlechts bei Hydatina: A. m. A., XLIX.

OBST, P., ^9. Untersuchungen liber das Verhalten der Nucleolen, etc. : Z. w. Z. LXVI., 2. — Ogata, 83. Die Veranderungen der Pancreaszellen bei der Secretion: A. A. P. — Oppel, A., '92. Die Befruchtung des Reptilieneies : A. m. A. XXXIX.— Osterhout, W. J. V., W. Uber Entstehung der karyokinetischen Spindel bei Equisetum: Jahrb. wiss. Bot., XXX. — Oltmanna, P., '95. Uber die Entwickelung der Sexualorgane bei Vaucheria: Flora. — Overton, C. E., , 88. Uber den Conjugationsvorgang bei Spirogyra: Ber. deutsch. Bot. Ges., VI. — Id., W. Beitrag zur Kenntniss der Gattung Volvox : Bot. Centralb., XXXIX.— Id., '93. Uber die Reduktion der Chromosomen in den Kernen der Pflanzen : Vierteljahrschr, naturf. Ges. Zurich, XXXVIII. Also Ann. Bot., VII., 25.

PALADINO, G., '90. I ponti intercellulari tra V uovo ovarico e le cellule follicolari, etc. : A. A., V. — Paulmier, P. C, '98. Chromatin Reduction in the Hemiptera: A. A., XIV. — Id., '99. The Spermatogenesis of Anasa tristis: /. M., XV., Suppl. — Peter, K., '99. Das Centrum flir die Flimmer- und Geisselbewegung: A. A., XV., 14, 15. — Pfeffer, W., '99. Uber die Erzeugung und die physiologische Bedeutung der Amitose : Ber. konigl., sacks., Ges. Hiss. Leipzig., July 3. — Pfitzner, W., '82. Uber den feineren Bau der bei der Zelltheilung auffretenden fadenformigen DifFerenzierungen des Zellkerns : M. J., VII. — Id., '83. Beitrage zur Lehre vom Baue des Zellkerns und seinen Theilungserscheinungen : A. m. A., XXII. — Pfliiger, E., '83. Uber den Einfluss der Schwerkraft auf die Theilung der Zellen : I., Arch. ges. Phys., XXXI.; II., Ibid., XXXII.; abstract in Biol. Centb., III., 1884. — Id., '84. Uber die Einwirkung der Schwerkraft und anderer Bedingungen auf die Richtung der Zelltheilung: Arch. ges. Phys., XXXIV. — Id.* '89. Die allgemeinen Lebenserscheinungen : Bonn. — Platner, G., '86, 1. Zur Bildungder Geschlechtsprodukte bei den Pulmonaten : A. m. A., XXVI. — Id., '86,2. — Uber die Befruchtung von Arion empiricorum : A. m. A., XXVII. — Id., '89, 1. Uber die Bedeutung der Richtungskorperchen : B. C, VIII. — Id., '89, 2. Beitrage zur Kenntniss der Zelle und ihrer Teilungserscheinungen, I. -VI. : A. m. A., XXXIII. — Poirault and Raciborski, '96. Uber konjugate Kerne und die konjugate Kerntheilung : B. C, XVI., 1. — Prenant, A., '94. Sur le corpuscule central: Bull. Soc. Sci. % Nancy, 1894. — Id., "98, '99. Sur le protoplasma superieure (archoplasme, kinoplasme, ergastoplasme) : Jour. Anal. Phys.,XXX\V., XXXV. — Preusse, P., '95. Uber die amitotische Kerntheilung in den Ovarien der Hemipteren : Z. w. Z., LIX., 2. — Provost and Dumas, *24. Nouvelle the'orie de la generation: Ann. Sci. Nat., I., II. — Pringsheim, N., '55. Uber die Befruchtung der Algen : Monatsb. Bert. Akad., 1855-56.

RABL, C, '85. Uber Zellteilung: M. /., X. — Id., '89, 1. Uber Zelltheilung: A. A., IV. — Id., '89,2. Uber die Prinzipien der Histologic: Verh. Anal. Ges., III. — vom Rath, O., '91. Uber die Bedeutung der amitotischen Kernteilung imHoden: Zo'ol. Anz., XIV. — Id., '92. Zur Kenntniss der Spermatogenese von Gryllotalpa vulgaris: A. m. A., XL. — Id., '93. Beitrage zur Spermatogenese von Saiamandra: Z. w. Z., LVII. — Id., '94. Uber die Konstanz der Chromosomenzahl bei Tieren : B. C, XIV., 13. — Id., "95, 1. Neue Beitrage zur Frage der Chromatinreduction in der Samen- und Eireife : A. m. A., XLVI. — Id., '95, 2. Uber den feineren Bau der Drusenzellen des Kopfes von Anilocra, etc. : Z. w. Z., LX., 1. — Rauber, A., ? 83. Neue Grundlegungen zur Kenntniss der Zelle : M.J.,


VIII. — Rawitz, B., '95. Centrosoma und Attraktionsphare in der ruhenden Zelle des Salamanderhodens : A. m. A., XLIV., 4. — Id., '97. Bemerkungen uber Mikrotomschneiden, etc. : A. A., XIII. — Reinke, Pr., '94. Zellstudien, I., A. m. A., XLIII. : III., Ibid., XLIV., 1894. — Id., '95. Untersuchungen uber Befruchtung und Furchung des Eies der Echinodermen : Sitz.-Ber. Akad. d. Wiss. Berlin, 1895, June 20. — Reinke and Rodewald, '81. Studien tiber das Protoplasma: (J titer such. aus. d. bot. Inst. Gdttingen, II. — Remak, R., '41. Uber Theilung rother Blutzellen beim Embryo: Med. Ver. Zeit., 1841. — Id., ^50-55., Untersuchungen uber die Entwicklung der Wirbelthiere : Berlin, 1850-55. — Id., '58. tiber die Theilung der Blutzellen beim Embryo: Mailer's Arch.* 1858.— Retzius, G., '89. Die Intercellularbrucken des Eierstockeies und der Follikelzellen : Vcrh. Anal. Ges. y 1889. — Rhumbler, L., '93. Uber Entstehung und Bedeutung der in den Kernen vieler Protozoen und im Keimblaschen von Metazoen vorkommenden Binnenkorper (Nucleolen) : Z, w. Z., LV1. — Id., '96. Versuch einer mechanischen Erklarung der indirekten Zell- und Kerntheilung : Arch. Eniwm., III. — Id., '97. Stemmen die Strahlen der Astrosphare oder ziehen sie? Arck. Entwm., IV. — Rompel, '94. Kentrochona Nebaliae n. sp., ein neues Infusor aus der Familie der Spirochoninen. Zugleich ein Beitrag zurLehre von der Kernteilung und dem Centrosoma : Z. w. Z., LVIII., 4. — Rosen, ^92. Uber tinctionelle Unterscheidung verschiedener Kernbestandtheile und der Sexual-kerne : Cokns Beitr. z. Biol. d. Pflanzen,\ . — Id., '94. Neueres liber die Chromatophilie der Zellkerne : Schles. Ges. vaterl. Kidt., 1894. — Roux, W., '83, 1. Uber die Bedeutung der Kernteilungsfiguren : Leipzig. — Id., '83, 2. Uber die Zeit der Bestimmung der Hauptrichtungen des Froschembryo : Leipzig. — Id., '85. t?ber die Bestimmung der Hauptrichtungen des Froschembryos im Ei, und tiber die erste Theilung des Froscheies : Breslauer drtzl. Zeitg., 1885. — Id., '87. Bestimmung der medianebene des Froschembryo durch die Kopulationsrichtung des Eikernes und des Spermakernes : A.m. A., XXIX. — Id., '88. tiber das kunstliche Hervorbringen halber Embryonen durch Zerstorung einer der beiden ersten Furchungskugeln, etc. : Virchow*s Archiv, 114. — Id., '90. Die Entwickelungsmechanik der Organismen. IVien, 1890. — Id., 7 92, 1. Entwickelungsmechanik : Merkel and Bonnet* Erg., II. — Id., '92, 2. Uber das entwickelungsmechanische Vermogen jeder der beiden ersten Furchungszellen des Eies: Verh. Anal. Ges., VI. — Id., *93, 1. t*ber Mosaikarbeit und neuere Entvvickelungshypothesen : An. Hefte, Feb., 1893. — Id., '93, 2. Cber die Spezifikation der Furchungzellen, etc. : B. C, XIII., 19-22

— Id., '94, 1. t!ber den " Cytotropismus " der Furchungszellen des Grasfrosches : Arch. Entwm., I., i, 2. — Id., '94, 2. Aufgabe der Entwickelungsmechanik, etc.: Arch. Entwm., I., 1. Trans, in Biol. Lectures, Wood's Holl, 1894. — Ruckert. J., '91. Zur Befruchtung des Selachiereies : A. A., VI. — Id., '92,1. Zur Entwicklungsgeschichte des Ovarialeies bei Selachiern : A. A., VII. — Id., '92, 2. Uber die Verdoppelung der Chromosomen im Keimblaschen des Selachiereies: Ibid., VIII.

— Id., '93, 2. Die Chromatinreduktion der Chromosomenzahl im Entwicklungsgang der Organismen : Merkel and Bonnets Erg., III. — Id., '94. Zur Eireifung bei Copepoden : An. Hefte. — Id., '95, 1. Zur Kenntniss des Befruchtungsvorganges: Sitsb. Bayer. Akad. IViss., XXVI., 1. — Id., '95,2. Zur Befruchtung von Cyclops strenuus : A. A., X., 22. — Id., ? 95, 3. t'ber das Selbstandigbleiben der vaterlichen und mutterlichen Kernsubstanz wahrend der ersten Entwicklung des befruchteten Cyclops-Eies : A. m. A., XLV., 3. — Riige. G., '89. Vorgange am Eifollikel der \virbelthiere : M.J., XV. —Ryder, J. A., '83. The Microscopic Sexual Characteristics of the Oyster, etc., Bull. U. S. Fish. Comm., March 14, 1883. Also, Ann. Mag. iVat. Hist., XII., 1883.


', M., '97. Beitrage zur Kenntniss der Chromatinreduktion in der Ovogenesis von Ascaris: Bull. Soc. Nat., Moscow, 1. — Sab a tier, A., '90. De la Spermatog^nese chez les Locustides: Comptes Rend., CXI., '90. — Sachs, J., '82. Vorlesungen liber Pflanzen-physiologie : Leipzig. — Id. Uber die Anordnung der Zellen in jlingsten Pflanzentheile : Arb. Bot. Inst. Wiirzburg, II. — Id., ^92. Physiologische Notizen, II., Beitrage zur Zellentheorie : Flora, 1892, Heft I. — Id., '93. Stoffund Form der Pflanzen-organe : Gcsammelte Abhandlungen, II., 1893. — Id., 35. Physiologische Notizen, IX., weitere Betrachtungen liber Energiden und Zellen : Flora, LXXXI., 2. — Sala, L., '95. Experimentelle Untersuchungen iiber die Reifung und Befruchtung der Eier bei Ascaris megalocephala : A. m. A., XL. — Sargant, Ethel, '95. Some details of the first nuclear Division in the Pollen-mother-cells of folium mar/agon: Journ. Roy. Mic. Soc, 1895, P art *3« 

— Id., '96. The Formation of the Sexual Nuclei in Lilium, I., Oogenesis: Ann. Bot., X. — Id., W. Same title, II., Spermatogenesis : Ibid., XI. — SchaVfer, E. A.,

  • 91. General Anatomy or Histology: in Quain's Anatomy, I., 2, 10th ed., London.

— Schaffner, J. H., '97, 1. The Life-history of Sagittaria: Bot. Gaz., XXIII., 4. — Id., '97, 2. The Division of the Macrospore Nucleus (in Lilium) : Ibid., XXIII., 6. — Id., '98. Karyokinesis in Root-tips of Allium : Ibid., XXVI., 4. — Schaudinn, P., '95. Uber die Theilung von Amoeba binucleata Gruber : Sit z. -Ber. Ges. Naturforsch. Freunde, Berlin, Jahrg. 1895, No. 6. — Id., ^96, 1. Uber den Zeugungskreis von Paramosba Eilhardi: Sitz.-Ber. Akad. Wiss., Berlin, 1896, Jan. 16. — Id., '96, 2. Uber die Copulation von Actinophrys Sol: Ibid. — Id., "96, 3. Uber das Centralkorn der Heliozoen : Verh. D. Zo'dl. Ges. — Schewiakoff, W., , 88. U ber die karyokinetische Kerntheilung der Eusfypha alveolata: J/./., XIII.

— Id., '93. Uber einen neuen Bakterienahnlichen Organismus: Hab. Schrift, Heidelberg, Winter. — Schieffer decker and Kossel, '91. Die Gewebe des Menschlichen Korpers: Braunschweig. — Schimper, '85. Untersuchungen iiber die Chlorophyllkorper, etc. : Zeitsch. wiss. Bot., XVI. — Schleicher, W., '78. Die Knorpelzelltheilung. Ein Beitrag zur Lehre der Theilung von Gewebezellen : Centr. med. Wiss. Berlin, 1878. Also A. m. A., XVI., 1879. — Schleiden, M. J., '38. Beitrage zur Phytogenesis : Mullens Archiv, 1838. [Trans, in Sydenham Soc, XII.: London, 1847.] — Schloter, G., '94. Zur Morphologie der Zelle: A. m. A., XLIV., 2. — Schmitz, '84. Die Chromatophoren der Algen. — Schneider, A., *73. Untersuchungen iiber Plathelminthen : Jahrb. d. oberhess. Ges. f. Natur-Heilkunde, XIV., Giessen. — Schneider, C, '91. Untersuchungen liber die Zelle: Arb. Zo'dl. Inst. Wien, IX., 2. — SchottlMnder, J., m Uber Kern und Zelltheilungsvorgange in dem Endothel der entziindeten Hornhaut: A. m. A., XXXI. — Schottl&nder, P., '93. Beitrage zur Kenntniss des Zellkerns, etc: Cohn's Beitrage, VI. — Schultze, Max, '61. Uber Muskelkorperchen und das was man eine Zelle zu nennen hat: Arch. Anat. Phys., 1861. — Schultze, O., '87. Untersuchungen iiber die Reifung und Befruchtung des Amphibien-eies : Z. w. Z., XLV. — Id., '90. Uber Zelltheilung: Sitzb. phys. med. Ges. Wiirzburg. — Id.,

  • 94. Die klinstliche Erzeugung von Doppelbildungen bei Froschlarven, etc. : Arch.

Entwm., I., 2. — Schwann, Th., '39. Mikroscopische Untersuchungen iiber die Ubereinstimmung in der Structur und dem Wachsthum der Thiere und Pflanzen: Berlin. [Trans, in Sydenham Soc, XII.: London, 1847.] — Schwarz, Fr., '87. Die Morphologische und chemische Zusammensetzung des Protoplasmas : Brcslau.

— Schweigger-Seidel, O., '65. Uber die Samenkorperchen und ihre Entwickelung: A. m. A., I. — Sedgwick, A.. 'SS-'SS. The Development of the Cape Species of Peripatus, I.-VI. : Q. J., XXV.-XXVIII. — Id., '94. On the Inadequacy of the Cellular Theory of Development, etc: Ibid., XXXVII., 1. — Seeliger, O., '94. Giebt es geschlechtlicherzeugte Organismen ohne miitterliche Eigenschaften ? : A. Ent., I., 2. — Selenka, E., '83. Die Keimblatter der Echinodermen : Studien




iiber Entwick., II., Wiesbaden, 1883. — Sertoli, B., '65. Dell* esistenza di particolari cellule ramificate dei canaliculi seminiferi del testicolo umano : 11 Margagni.

— Shaw, W. R., '98, 1. Uber die Blepharoplasten bei Onoclea und Marsilia: Ber. D. Bot. Ges., XVI., 7. — Id., '98, 2. The Fertilization of Onoclea : Ann. B<*^ XII., 47. — Siedlecki, M., '95. Uber die Struktur und Kerntheilungsvorgange bei den Leucocyten der Urodelen : Anz. Akad. IViss., Krakau, 1895. — Id., ' f 9S. £tude cytologique et cycle eVolutif de Adelea: Ann. Inst. Pasteur., XIII. — Sobotta, J., '95. Die Befruchtung und Furchung des Eies der Maus: A. m. A., XLV. — Id., '97. Die Reifung und Befruchtung des Eies von Amphioxus : Ibid., L. — Solger, B., '91. Die radiaren Strukturen der Zellkorper im Zustand der Ruhe und bei der Kerntheilung : Bert. Klin. Wochenschr., XX., 1891. — Spallanzani, 1786. Experiences pour servir a l'histoire de la gdn^ration des animaux et des plantes : Geneva. — Spitzer, '97. Die Bedeutung gewisser Nucleoproteide fur die oxvdative Leistung der Zelle: Arch. ges. Phys., LX VI I. — Stevens, W. C, *98. Ober Chromosomentheilung bei der Sporenbildung der Fame: Ber. D. Bot. Ges., XVI., 8. — Stevens, F. L., '99. The compound Oosphere of Albugo: Bot. Gas., XXVIII., 3,4.

— Strasburger, B., '75. Zellbildung und Zelltheilung : 1st ed., Jena* 1875. — IcL '77. t v ber Befruchtung und Zelltheilung: /. Z., XL — Id., '80. Zellbildung und Zellteilung: 3d ed. — Id., '82. Cber den Theilungsvorgang der Zellkerne und das Verhaltniss der Kerntheilung zur Zelltheilung: A. m. A., XXI. — Id., '84, 1. Die Controversen der indirecten Zelltheilung: Ibid., XXIII. — Id., '84, 2. Neue Untersuchungen liber den Befruchtungsvorgang bei den Phanerogamen, als Grundlage fur eine Theorie der Zeugung : Jena, 1884. — Id., '88. tlber Kern- und Zellteilung im Pflanzenreich, nebst einem Anhang liber Befruchtung: Jena. — Id., '89. V ber das Wachsthum vegetabilischer Zellhaute: Hist. Bei., II. , Jena. — Id., '91. Das Protoplasma und die Reizbarkeit : Rektoratsrede, Bonn, Oct. 18, 1891. Jena, Fischer. — Id., '92. Histologische Beitrage, Heft IV. : Das Verhalten des Pollens und die Befruchtungsvorgange bei den Gymnospermen, Schwarmsporen, pnanzliche Spermatozoiden und das Wesen der Befruchtung: Fischer, Jena, 1892. — Id., *93, 1. Cber die Wirkungssphare der Kerne und die Zellengrosse : Hist. Beitr., V. — Id.. "93, 2. Zu dem jetzigen Stande der Kern- und Zelltheilungsfragen : A. A.., VIII., p. 177. — Id., '94. Cber periodische Reduktion der Chromosomenzahl im Entwicklungsgang der Organismen : B. C, XIV. — Id., '95. Karyokinetische Probleme : Jahrb. f. tuiss. Botanik, XXVI II., 1 . — Id., '97, 1. Kerntheilung und Befruchtung bei Fucus : Jahrb. iviss. Bot., XXX. —Id., 97, 2. fber Befruchtung: Ibid. — Id., ^97, 3. Cber Cytoplasmastrukturen, Kern- und Zelltheilung: Ibid. — Id., -98. Die Pflanzlichen Zellhaute: Ibid., XXXI. — Strasburger and Mottier, '97. Cber den zweiten Theilungsschritt in Pollenmutterzellen : Ber. D. Bot. Ges., XV., 6. — Van der Stricht, O., 92. Contribution a l'e'tude de la sphere attractive: A. /?., XII., 4. — Id., '95, 1. La maturation et la fe'condation de l"ceuf d\Amphioxus lanceolatus: Bull. Acad. Roy. Belgique, XXX.. 2. — Id., ? 95, 2. De l'origine de la figure achromatique de l'ovule en mitose chez le Thysanozoon Brocchi : Verhandl. d. anat. lersamml. in Strassburg, 1895, p. 223. — Id., '95, 3. Contributions a Te'tude de la forme, de la structure et de la division du noyau : Bull. Acad. Roy. Sc. Belgique, XXIX. — Id.. "98, 1. La formation des globules polaires, etc., chez Thysanozoon Arch. Biol., XV. — Id., '98, 2. Contribution a Te'tude du noyau vitellin de Balbiani \ T erh. An. Ges., XII. — Strieker, S., '71. Handbuch der Lehre von den Geweben Leipzig. — Stuhlmann, Fr., 86. Die Reifung des Arthropodeneies nach Beobach tungen an Insekten, Spinnen, Myriopoden und Peripatus : Ber. Naturf. Ges. Fretburg, I. — Suzuki, B., '98. Notiz liber die Entstehung des Mittelstlickes von Selachiern : A. A., XV., 8. — Swaen and Masquelin. '83. lStude sur la Spermatogdnese: A. B., IV. — Swingle, W. T., '97. Zur Kenntniss der Kern- und Zellteilungen bei den Sphacelariaceae : /. w. B., XXX.


THOMA, R„ , 9€. Text-book of General Pathology and Pathological Anatomy : Trans, by A. Bruce, London. — Thomson, Allen. Article 4i Generation " in Todd's Cyclopaedia. — Id. Article "Ovum" in Todd's Cyclopaedia. — Townsend, C. O.,

  • 97. Der Einfluss des Zellkerns auf die Bildung der Zellhaut : Jahrb. wiss. Bo/.,

XXX. — Treat, Mary, '73. Controlling Sex in Butterflies: Am. Nat., VII.— Trow, A. H., ^95. The Karyology of Saprolegnia: Ann. Bot., IX. — Tyson, James, '78. The Cell-doctrine : 2d ed., Philadelphia.

UNNA, P., '95. Vber die neueren Protoplasmatheorien, und das Spongioplasma: Deutsche Med. Zeit., 1895, 98-100. — Ussow, M., '81. Untersuchungen liber die Entwickelung der Cephalopoden : Arch. Biol., II.

VEJDOVSK^, F., '88. Entwickelungsgeschichtliche Untersuchungen, Heft I. : Reifung, Befruchtung und Furchung des Rhynchelmis-Eies : Prag, 1888. Vejdovsky and MrAzek, '98. Centrosom und Periplast : Sitzber. b'dhm. Ges. Wiss. — Verworn, M., '88. Biologische Protisten-studien : Z. w. Z., XLVI. — Id., '89. Psychophysiologische Protisten-studien : Jena. — Id., ^l. Die physiologische Bedeutung des Zellkerns : Pfliiger^s Arch.f. d. ges. Physiol., II. — Id., "95. Allgemeine Physiologie : Jena . — Virchow, R., '55. Cellular-Pathologie : Arch. Path. Anal. Phys., VIII., 1. — Id., '58. Die Cellularpathologie in ihrer Begriindung auf physiologische und pathologische Gewebelehre : Berlin, 1858. — De Vries, H., '89. Intracellulare Pangenesis : Jena.

WAGER, H., '96. On the Structure and Reproduction of Cystopus. Ann. Bot., X. — Waldeyer, W., '70. Eierstock und Ei : Leipzig.— Id., '87. Bau und Entwickelung der Samenfaden : Verh. An. Ges. Leipzig 1887. — Id., '88. tlber Karyokinese und ihre Beziehungen zu den Befruchtungsvorgangen : A. m. A.,XXXU. [Trans, in Q»J^\ — Id., '95. Die neueren Ansichten liber den Bau und das Wesen der Zelle: Deutsch. Med. Wochenschr., No. 43, ff., Oct. fF., 1895. — Warneck, N. A., '50. Uber die Bildung und Entwickelung des Embryos bei Gasteropoden : Bull. Soc. Imp. Nat. Moscou, XXIII., 1. — Watase\ S.. '91. Studies on Cephalopods; I., Cleavage of the Ovum: /. M., IV., 3. — Id., '92. On the Phenomena of Sex-difFerentiation : Ibid., VI., 2, 1892. — Id., ^3, 1. On the Nature of Cellorganization: IVood's Holl Biol. Lectures, 1893. — Id., ^3, 2. Homology of the Centrosome : /. M., VIII., 2. — Id., '94. Origin of the Centrosome : Biological Leetures, Wood*s Holl, 1894. Webber, H. J., '97. 1. Peculiar Structures occurring in the Pollen-tube of Zamia: Bot. Gazette. XXIII., 6. — Id., '97, 2. The Development of the Antherozoids of Zamia: Ibid., XXIV., 1. — Id., '97, 3. Notes on the Fecundation of Zamia and the Pollen-tube Apparatus of Gingko: Ibid., XXIV., 4. — Weismann, A., '83. Ober Vererbung: Jena. — Id., '85. Die Kontinuitat des Keimplasmas als Grundlage einer Theorie der Vererbung: Jena. — Id., '86, 1. Richtungskorper bei parthenogenetischen Eiern : Zool. Anz., No. 233. — Id., '86, 2. Die Bedeutung der sexuellen Fortpflanzung fur die Selektionstheorie : Jena. — Id.. '87. Cber die Zahl der Richtungskorper und liber ihre Bedeutung fur die Vererbung : Jena. — Id., '91, 1. Essays upon Heredity, First Series: Oxford. — Id., ^1, 2. Amphimixis, oder die Vermischung der Individuen: Jena, Fischer. — Id, 1 92. Essays upon Heredity, Second Series: Oxford, 1892. — Id., ^3. The Germ-plasm: New York. — Id., '94. Aussere Einflusse als Entwicklungsreize : Jena. — Id., "99. Regeneration: Nat. Sci., XIV., 6. [See also A. A., 1899.] "Wheeler, W. M., '89. The Embryology of Blalta Germanica and Doryphora decemlineata : J. M., III. — Id., "93. A Contribution to Insect-embryology: Ibid., VIII., 1. — Id., '95. The Behaviour of the Centrosomes in the Fertilized Egg of Myzostoma glabrum: Ibid., X. — Id., '96. The Sexual Phases of Myzostoma:


Mitth. ZooL St. Neapel, XII., 2. — Id., W. The Maturation, Fecundation, and early Cleavage in Myzostoma: Arch. Biol., XV. — "Whitman, C. O., '78. The Embryology of Clepsine: Q. J., XVIII. — Id., '87. The Kinetic Phenomena of the Egg during Maturation and Fecundation : /. M., I., 2. — Id., *88. The Seat of Formative and Regenerative Energy : Ibid., II. — Id., "93. The Inadequacy of the Cell-theory of Development : WoocTs H oil Biol. Lectures, 1893. — Id., 1*4. Evolution and Epigenesis : Ibid., 1894. — Wiesner, J., '92. Die Elementarstruktur nnd das Wachstum der lebenden Substanz: Wien. — "Wilcox, E. V., *95. Spermatogenesis of Caloptenus and Cicada : Bull, of the Museum of Comp. ZooL, Harvard College, Vol. XXVII., No. 1. — Id., '96. Further Studies on the Spermatogenesis of Caloptenus : Bull. Mus. Comp. ZooL, XXIX. —Will, L., '86. Die Entstehung des Eies von Colymbetes: Z. w. Z, XLIII. — Wilaon, Bdm. B., ^92. The Celllineage of Nereis: f. M., VI., 3. — Id., "93. Amphioxus and the Mosaic Theory of Development : Ibid., VIII., 3. — Id., '94. The Mosaic Theory of Development: Wood^s Holl Biol. Led.* 1894. — Id., '95, 1. Atlas of Fertilization and Karyokinesis: New York* Macmillan. — Id., '95, 2. Archoplasm, Centrosome, and Chromatin in the Sea-urchin Egg: /. M., XI. — Id., '96. On Cleavage and Mosaic-work. [Appendix to Crampton and Wilson, '96.] : A. Entivm.^ III.. 1.— Id., '97. Centrosome and Middle-piece in the Fertilization of the Egg. Science* Vol. V., No. 114. — Id., '98. Considerations on Cell-lineage and ancestral Reminiscence: Ann. N. Y. Acad. Sci., XI. See also Wood? s Holl Biol. Lectures, '99. — Id., '99. On protoplasmic Structure in the Eggs of Echinoderms and some other Animals: /. M., XV. Suppl. — Wilson and Mathews, ^5. Maturation, Fertilization, and Polarity in the Echinoderm Egg: /. M., X., 1. — "Wolff, Caspar Friedrich, 1759. Theoria Generationis. — Wolff, Gustav, ^94. Bemerkungen zum Darwinismus mit einem experimentellen Beitrag zur Physiologie der Ent wicklung: B, C, XIV., 17. — Id., '95. Die Regeneration der Urodelenlinse : Arch. Entwtn., 1., 3. — Wolters, M., '91. Die Conjugation und Sporenbildung bei Gregarinen : A. m. A., XXXVII. — Woltereck, R., '98. Zur Bildung und Entwicklung des Ostrakoden-Eies : Z. w. Z., LXIV.

TUNG, B.. '81. De Tinfluence de la nature des aliments sur la sexualite' : C. R., XCIII ; also Arch. Exp. ZooL, 2d, I., 1883.

ZACH ARIAS. O., '85. If ber die amoboiden Bewegungen der Spermatozoen von Polyphemus pediculus : Z. w. Z., XLI. — Zacharias. E.. "93, 1. Cber die chemische Beschaffenheit von Cytoplasma und Zellkern : Ber. deutsch. Bot. Ges.. II., 5. — Id., '93, 2. Cber Chromatophilie : Ibid., 1893. — Id., '95. t'ber dns Verhalten des Zellkerns in wachsenden Zellen : Flora, 81, 1895. — Id., '94. Tber Beziehungen des Zellenwachstums zur Beschaffenheit des Zellkerns : Bcrichte der deutschen bot an. Gesellschaft, XII., 5. — Id., '98. Cber Nachweis und Vorkommen von Nuclein: Bcr.d. Bot. Ges., XVI., 7. — Ziegler, E., '88. Die neuesten Arbeiten liber Vererbung und Abstammungslehre und ihre Bedeutung fur die Pathologie: Beitr. zur path. Anat., IV. — Id., , 89. t*ber die Ursachen der pathologischen Gewebsneubildungen : ////. Beitr. zur. wiss. Med. Festschrift, R. Virchmv, II.— Id., '92. Lehrbuch der allgemeinen pathologischen Anatomie und Pathogenese. 7th ed., Jena. — Ziegler, H. E., '87. Die Entstehung des Blutes bei Knochenfischenembryonen : A. m. A. — Id., '91. Die biologische Bedeutung der amitotischen Kerntheilung im Tierreich : B. C, XI. — Id., '94. t v ber das Verhalten der Kerne im Dotter der meroblastischen Wirbelthiere : Ber. Naturf Ges. Freiburg, 1894.— Id., '95. Untersuchungen liber die Zelltheilung : Vcrhandl. d. deutsch. ZooL Ges., 1895. — Id., '96. Einige Betrachtungen zur Entwicklungsgeschichte der Echinodermen : Verh. d. ZooL Ges. — Id., '98. Experimented Studien iiber die Zellthei


lung, I., II. : Arch. Entwm., VI., 2. — Ziegler and vom Rath. Die amitotischc Kerntheilung bei den Arthropoden : B. C, XI. — Zimmermann, A., *93, 1. Beitrage zur Morphologie und Physiologie der Pflanzenzelle : Tubingen. — Id., "94. Sammelreferate aus dem Gesammtgebiete der Zellenlehre: Bot. Centb. Beihefte* 1894. Zimmermanu, K. W., 93, 2. Studien liber Pigmentzellen, etc. : A. m. A , XLI. — Id, *98. Beitrage zur Kenntniss einiger Driisen und Epithelzellen : A. m. A.* LII. — Zoja, R., ^95, 1. Sullo sviluppo dei blastomeri isolati dalle uova di alcune meduse : A. Entwm., I., 4 ; II., 1 : II., IV. — Id., *95, 2. Sulla independenza della cromatina paterna e materna nel nucleo delle cellule embrionali: A. A.* XI., 10. Id., '97. Stato attuale degli Studii sulla Fecondazione : Boll. Sci. di Pavia, XVIII., XIX.— Zur Strassen, O., '98. Uber die Riesenbildung bei AscarisEiern: Arch. Entwm., VII., 4.



■ l ■'r ■


■-:i -\





i i




■ i


Albrecht, nuclei, 32.

Altmann, granule-theory, 25, 27, 290; nu clein, 332. Amici, pollen-tube, 218. Andrews, spinning activities, 61. Apathy, nerve-cells, 48. Aristotle, epigenesis, 8. Arnold, fibrillar theory of protoplasm, 23;

leucocytes, 117; nucleus and cytoplasm,

3<>3Atkinson, reduction, 269.

Auerbach, 6; double spermatozoa, 142;

staining-reactions, 176; fertilization, 181.

Von Baer, cleavage, 10; cell-division, 64; egg-axis, 378; development, 396.

Balbiani, scattered nuclei, 40 ; spiremenuclei, 36; mitosis in Infusoria, 88; chromatin-granules, 1 12; yolk-nucleus, 155156; regeneration in Infusoria, 343.

Balfour, polar bodies, 243; rate of division, 366; unequal division, 371.

Ballowitz, structure of spermatozoa, 139, 140; double spermatozoa, 142.

Van Bambeke, deutoplasm and yolk -nucleus, 156-160; elimination of chromatin, 155.

Barry, fertilization, 181.

De Bary, protoplasm, 4, 5, 20; conjugation, 181 ; cell-division and growth, 393.

Beale, cell-organization, 291.

Bechamp and Estor, microsome-theory, 290, 291.

Belajeff, spermatozoids, 172-175; reduction in plants, 267.

Benda, spermatogenesis, 163; Sertoli-cells, 284.

Van Beneden, cell-theory, I, 6, 7; protoplasm, 23; nuclear membrane, 38; centrosome and attraction-sphere, 51, 74, 77, 310, 323; cell-polarity, 55; cell-division, 64, 74; origin of mitotic figure, 74-77; theory of mitosis, 100; division of chromosomes, 112; fertilization of Ascaris, 7, 182; continuity of centrosomes, 75; germ

nuclei, 205; centrosome in fertilization, 208; theory of sex, 243 ; parthenogenesis, 281 ; nucleus and cytoplasm, 303; nuclear microsomes, 302; promorphology of cleavage, 381; germinal localization, 399.

Van Beneden and Julin, first cleavage- plane, 380.

Bergmann, cleavage, 10; cell, 17.

Bernard, Claude, nucleus and cytoplasm, 341 ; organic synthesis, 431.

Berthold, protoplasm, 42 ; cell-division,

37°Bickford, regeneration in coelenterates, 392,


Biondi, Sertoli-cells, 284.

Biondi-Ehrlich, staining-fluid, 157.

Bischoff, cell, 17.

Bizzozero, cell-bridges, 60.

Blanc, fertilization of trout, 210.

Blochmann, insect-egg, 132; budding of nucleus, 155; polar bodies, 281 ; bilaterality of ovum, 383.

Bohm, fertilization in fishes, 192.

Bolsius, nephridial cells, 47.

Bonnet, theory of development, 8, 432.

Born, chromosomes in Triton-tgg t 338; gravitation-experiments, 386.

Boveri, centrosome, named, 51 ; a permanent organ, 51, 74; in fertilization, 192, 211, 215, 230; structure, 309; functions, 354; archoplasm, 69, 318; origin of mitotic figure, 74, 77, 319; varieties of A scar is, 87; theory of mitosis, 101, 108; division of chromosomes, 112; origin of germ-cells, 147; fertilization of Ascaris, 182; of Pterotrachca, 184; of Echinus, 192; theory of fertilization, 190, 21 1; of parthenogenesis, 281 ; partial fertilization, 190, 194; reduction, 233; maturation in Ascaris, 238; tetrads, 238; centriole, 309; attraction-sphere, 324; egg-fragments, 353.

Braem, cell-division, 377.

Brandt, symbiosis, 53; regeneration in Protozoa, 342.

47 ]



Brauer, bivalent chromosomes, 82; mitosis in rhizopod, 96; fission of chromatin granules, 113; deutoplasm, 153; fertilization in Branchipus, 192; parthenogenesis in Ar/emia, 281 ; spermatogenesis in Ascaris, 255; intra-nuclear centrosome, 304.

Bra us, 81.

Brogniard, pollen-tube, 218.

Brooks, heredity, 12; variation, 179.

Brown, Robert, cell-nucleus, 18; pollentube, 218.

Brucke, cell-organization, 289.

Von Brunn, spermatozoon, 141.

Buhler, astral systems, 318.

Biitschli, 6; protoplasm, 25,36, 50; diffused nuclei, 40; artifacts, 42; asters, 48, 316; cell-membrane, 54; mitosis, 109, no; centrosome in diatoms, 51; rejuvenescence, 178; polar bodies, 238.

Calberla, micropyle, 200.

Calkins, nuclei of flagellates, 40; mitosis in Noctiluca, 92; yolk-nucleus, 157; origin of middle-piece, 165; reduction, 253, 257.

Campbell, fertilization in plants, 216.

Carnoy, nucleus, 40; muscle-fibre, 48; centrosome, no; amitosis, 1 15, 117; germnuclei, 184; asters, 305, 317.

Carnoy and Le Brun, nucleoli, 130; fertilization, 211; reduction, 263.

Castle, egg-axis, 379; fertilization, 193.

Chittenden, organic synthesis, 341.

Chmielewski, reduction in Spirogyra, 280.

Chun, amitosis, 117; partial development of ctenophores, 418.

Clapp, first cleavage-plane, 381.

Coe, fertilization, 194, 213; centrosome, 321.

Cohn, cell, 17.

Conklin, size of nuclei, 71; union of germnuclei, 204; centrosome in fertilization, 210; centrosome and sphere, 323; unequal division, 373; protoplasmic currents, 377; cell-size and body-size, 388; types of cleavage, 423.

Corda, pollen-tube, 218.

Crampton, yolk-nucleus, 158; reversal of cleavage, 368; experiments on snail, 419, 421; on tunicates, 419.

Crato, protoplasm, 50.

Darwin, evolution, 2, 5 ; inheritance, 12, 396; variation, n ; pangenesis, 12, 290 ; gemmules, 290.

Darwin, F., protoplasmic fragments, 346.

Dendy, cell-bridges, 60.

Dogiel, amitosis, 118.

Driesch, dispermy, 198; fertilization of eggfragments, 200, 353; pressure-experiments, 375, 410; regeneration, 395; isolated blastomeres, 409; theory of development, 394, 415; experiments on ctenophores, 418; ferment -theory, 427.

Driiner, spindle-fibres, 79; central spindle, 105; aster, 321, 326.

Von Ebner, Sertoli-cells, 284.

Ehrlich, tar-colours, 335.

Eismond, structure of aster, 48.

Elssberg, plastidules, 291.

Endres, experiments on frog's egg, 399, 419.

Engelmann, ciliated cells, 44; rejuvenescence, 179.

Von Erlanger, asters, 48, 316; spindle, 81 ; elimination of chromatin, 155; Nebenkern, 163, 165; fertilization, 194, 212, 213; centroplasm, 324.

Eycleshymer, first cleavage-plane, 381.

Farmer, reduction in plants, 275.

Fick, fertilization of axolqtl, 192, 212.

Field, staining-reactions, 176.

Fischel, ctenophores, 419.

Fischer, nucleus, 40; artifacts, 42; stainingreactions, 335.

Flemming, protoplasm, 25, 27 ; chromatin, ^} ; centrosome, 51 ; cell-bridges, 60, 61 ; celldivision, 64, 70; splitting of chromosomes, 70; mitotic figure, 79 ; heterotypical mitosis, 86; leucocytes, 102; theory of mitosis, 106; division of chromatin, 113; amitosis, 117,285; nucleoli, 127; rotation of spernihead, 188; spermatogenesis, 259-262; astral rays, 317; germinal localization.

399. Floderus, follicle-cells, 150.

Fol, 1, 6, 64; amphiaster, 68; theory of mitosis, 108; sperm-centrosome, 191 ; polyspermy, 192; attraction -cone, 198; vitelline membrane, 199; asters, 316.

Foot, yolk-nucleus and polar rings, 156, 202; fertilization in earthworm, 187; entrancefunnel, 201; fertilization-centrosome, 212.

Foster, cell-organization, somacules, 291.

Francotte, polar bodies, 235; centrosome, 306; sphere, 312, 325.

Frommann, protoplasm, 23; nucleus and cytoplasm, 303.

Galeotti, pathological mitoses, 97. Gallardo. mitosis, 109.



Galton, inheritance, 9.

Gardiner, cell-bridges, 59; chromatin-elimi nation, 276; sphere, 325. Garnault, fertilization in Arion, 207. Geddes and Thompson, theory of sex, 124. Van Gehuchten, spireme-nuclei, 36; nuclear

polarity, 36; muscle-fibre, 48. Giard, polar bodies, 235, 238. Gierke, staining-reactions, 335. Gilson, spireme-nuclei, 36. Godlewski, spermatogenesis, 168. Graf, nephridial cells, 47. Gregoire, reduction, 267. Griffin, fertilization, centrosomes in Thalas sema, 193, 194, 213; reduction, 259;

structure of centrosome, 314; aster-formation, 321. Grobben, spermatozoa, 141. Gruber, diffused nuclei, 40; regeneration in

Stentor, 342. Guignard, mitosis in plants, 82; fertilization

in plants, 218, 221; reduction, 263, 267.

Haberlandt, position of nuclei, 346.

Hack el, inheritance, 7; epithelium, 56; cellstate, 58.

Hacker, polar spindles, 276; bivalent chromosomes, 88; nucleolus, 125, 128; primordial germ-cells, 148; gerin-nuclei, 208, 299; reduction in copepods, 249.

Hallez, promorphology of ovum, 384.

Halliburton, proteids, 331 ; nuclein, 333.

Hamm, discovery of spermatozoon, 9, 181.

Hammar, cell-bridges, 60.

Hammarsten, proteids, 331.

Hansemann, pathological mitoses, 97.

Hanstein, metaplasm, 19.

Hardy, artifacts, 42.

Harper, mitosis, 82.

Hartsoeker, spermatozoon, 9.

Harvey, inheritance, 7; epigenesis, 8.

Hatschek, cell-polarity, 56; fertilization, 179.

Heidenhain, nucleus, 36; basichromatin and oxychromatin, 38, 337; cell-polarity, 55; position of centrosome, 57; leucocytes, 102; theory of mitosis, 105; amitosis, 116; staining-reactions, 337; nuclear microsomes, 303; microcentrum, 311; asters, 311, 317; origin of centrosome, 315; position of spindle, 377.

Heider, insect-egg, 132.

Heitzmann, cell-bridges, 59; nucleus and cytoplasm, 303.

Henking, fertilization, 187; insect-egg, 96; spermatogenesis, 165, 248, 253, 271.

Henle, granules, 289.

Henneguy, deuto plasm, 153; yolk-nucleus, 160; centrosome, 356.

Hensen, rejuvenescence, 179.

Herbst, development and environment, 428.

Herla, independence of chromosomes, 208, 299.

Hermann, central spindle, 78, 105; division of chromatin, 112; spermatozoon, 165, 166; staining-reactions, 176.

Hertwig, O., 1, 7, 9; bivalent chromosomes, 88; pathological mitoses, 97; rejuvenescence, 178; fertilization, 181 ; middlepiece, 187; polyspermy, 199; paths of germ-nuclei, 204; maturation, 241 ; polar bodies, 238; inheritance, 182; laws of cell-division, 364; theory of development,

415Hertwig, O. and R., 197; egg-fragments,

199; polyspermy, 199.

Hertwig, R., mitosis in Protozoa, 90; germcells in Sagitta, 146; amphiasters in unfertilized eggs, 306; conjugation, 222; reduction in Infusoria, 277; in ActinospJuzrium, 278; origin of centrosome, 315; cell-division, 391. ,

Hill, fertilization, 187, 193.

Hirase, spermatozoids, 144; fertilization, 218.

His, germinal localization, 398.

Hofer, regeneration in Am<xba } 343.

Hoffman, micropyle. 200.

Hofmeister, cell-division and growth, 393.

Holmes, cleavage, 368.

Hooke, R., cell, 17.

Hoyer, amitosis, 115.

Huie, Drosera, 350.

Huxley, protoplasm, 5; germ, 7, 396; fertilization, 178, 231; evolution and epigenesis, 432.

Ikeno, cell-bridges, 150; blcpharoplasts, 173; fertilization, 221.

Ishikawa, Noctiiuca, mitosis, 92; conjugation, 227; reduction, 267; flagellum, 171.

Jennings, cleavage, 377.

Jordan, deutoplasm and yolk-nucleus, 153,

156; first cleavage-plane, 381. Julin, fertilization in Styltopsis, 192.

Keuten, mitosis in Eugtena, 91. Klebahn, conjugation and reduction in desmids and diatoms, 280.



Klebs, pathological mitosis, 97, 98; cellmembrane, 346.

Klein, nuclear membrane, 38; theory of mitosis, 100; amitosis, 118; nucleus and cytoplasm, 303; asters, 316.

Klinckowstrdm, fertilization, 213; reduction,

259. Von Kolliker, I, 6, 9, 10, 27; epithelium, 56;

cell-division, 63; spermatozoon, 9, 134;

inheritance, 182; development, 413.

Korff, spermatogenesis, 163, 168, 173.

Korschelt, nucleus, 37; amitosis, 115; movements and position of nuclei, 125, 349, 387; nurse-cells, 151; fertilization, 193; tetrads in Ophryotrocha, 258; physiology of nucleus, 348; polarity of egg, 387.

Kossel, chromatin, 336; nuclein, 334; organic synthesis, 340.

Kostanecki, fertilization, 193 ; astral rays, 318.

Kostanecki and Wierzejski, fertilization of Physa, 193, 210, 212; continuity of centrosomes, 211.

Kupffer, energids, 30; cytoplasm, 41.

Lamarck, inheritance, 12.

I*amarle, minimal contact-areas, 361.

Lankester, germinal localization, 398.

Lauterborn, mitosis in diatoms, 95; origin of centrosome, 315.

Leeuwenhoek, spermatozoon, 8; fertilization, 181.

Von Lenhossek, nerve-cell, 21, 47; spermatogenesis, 169, 315; centrosome, 314, 356.

Leydig, cell, 19; protoplasm, 20; cell-membrane, 54; spermatozoa, 142; elimination of chromatin, 159.

Lilienfeld, staining-reactions of nucleins, 336.

Lillie, fertilization, 196, 213; centrosome and aster, 312, 326, 327; regeneration in Stentor, 343 ; cleavage, 360, 369, 377.

Loeb, chemical fertilization, 215, 392; regeneration in ccclentcrates, 392; theory of development, 427; environment and development, 430.

Lustig and Galeotti, pathological mitoses, 98; centrosome, 51.

Maggi, granules, 290.

Malfatti, staining-reactions of nucleins, 335.

Mark, germ-nuclei, 204; polar bodies, 235;

polarity of ovum, 387. Mathews, pancreas-cell, 44; aster-formation,

no; fertilization of echinoderms, 192,212;

origin of centrosome, 125; nucleic acid,

334; staining-reactions, 337.

Maupas, sex in Rotifers, 145; rejuvenescence, 179; conjugation of Infusoria, 223.

Mayer, staining, 335.

McClung, spermatogenesis, 271.

MacFarland, spindle, 79; fertilization, 213, 214; centrosome and sphere, 312, 314,

321. McGregor, spermatogenesis, 167; reduction,

261. McMurrich, gasteropod development, 152;

metamerism in isopods, 390. Mead, fertilization of Chatopierus, 192, 194,

215; sperm-centrosome, 215; centrosomes

de novo, 212, 306; cell-division, 391. Merkel, Sertoli-cells, 284. Mertens, yolk-nucleus and attraction-sphere,

I5 6 » *59Metschnikoff, insect-egg, 383.

Meves, amitosis, 119, 285; spermatogenesis, 167, 169; reduction, 260; cilia, 357.

Meyer, energids, 30; cell-bridges, 60.

Miescher, nuclein, 332.

Mikosch, protoplasm, 44.

Minot, rejuvenescence, 179; cyclical division, 222; theory of sex, 243; Sertolicells, 284; parthenogen sis, 280.

Von Mohl, cell-division, 9; protoplasm, 17.

Montgomery, nucleolus, 34; spermatogenesis, 257, 271.

Moore, spermatozoon, 167, 171 ; reduction, 263.

Morgan, centrosomes, 307; fertilization of egg-fragments, 353; cell-division, 391; effect of fertilization, 201 ; numerical relations of cells, 389; regeneration, 393, 394; isolated blastomeres, 410; polarity, 417; experiments on ctenophores, 418; on frog's egg, 422.

Mottier, mitosis, 83; fertilization, 221; reduction, 266; asters, 305.

Munson, yolk -nucleus, 156.

Nageli, development, I; cell-organization, micella?, 289, 291 ; polioplasm, 41 ; idioplasm-theory, 401.

Nawaschin, fertilization, 218.

Nemec, mitosis, 82; yolk-nucleus, 159.

Newport, fertilization, 181; first cleavageplane, 380.

Nissl, chromophilic granules, 48.

Nussbaum, germ-cells, 122; sex, 145; regeneration in Infusoria, 342; nucleus, 426.

Obst, nucleoli, 130; follicle-cells, 151. Osterhout, spindle, 82; tetrads, 253.



Overton, germ-cells of Vohox, 134; conjugation of Spirogyra, 229; reduction, 274,

275Owen, germ-cells, 122.

Paladino, cell-bridges, 60.

Paul mier, spermatozoon, 165; reduction, 252, 271.

Peremeschko, leucocytes, 117.

Peter, cilia, 357.

Pfeffer, hyaloplasm, 41 ; amitosis, 119; chemotaxis of germ-cells, 197.

PHtzner, cell-bridges, 60; chromatin- granules, 112.

Pfluger, position of spindle, 375 ; first cleavage-plane, 380; gravitation-experiments, 386; isotropy, 378.

Plateau, minimal contact-areas, 366.

Platner, mitosis, no; egg-centrosome, 125; formation of spermatozoon, 163; fertilization of Arion, 20J; maturation, 241.

Pouchet and Chabry, development and environment, 428.

Prenant, spermatozoon, 162; archoplasm, 322.

Preusse, amitosis, 119.

Prevost and Dumas, cleavage, 10.

Pringsheim, Hautschicht, 41; fertilization, 181.

Purkinje, protoplasm, 17.

Rabl, nuclear polarity, 36; cell-polarity, 56; centrosome in fertilization, 210; individuality of chromosomes, 294; astral systems,

3<7Ranvier, blood-corpuscles, 54.

Vom Rath, bivalent chromosomes, 88; amitosis, 118, 225; early germ-cells, 149; reduction, 249.

Rauber, cell-division and growth, 393.

Rawitz, amitosis, 116; staining-reactions,

335Redi, genetic continuity, 290.

Reichert, cleavage, 10, 64.

Reinke, pseudo-alveolar structure, 50; nucleuses, 303; cedematin, 36; asters, 305; nucleus and cytoplasm, 303.

Remak, cleavage, 1, 10, 361; cell-division, 64; egg-axis, 378.

Retzius, muscle-fibre, 48; cell-bridges, 60; end-piece, 140.

Rhumbler, 105.

Robin, germinal vesicle, 64.

Rosen, staining-reactions, 220.

Roux, 245, 301, 351 ; meaning of mitosis, 244,

301 , 351, 405; position of spindle, 377; first cleavage-plane, 380; frog-experiments, mosaic theory, 399; theory of development, 405 ; post-generation, 408.

Ruckert, pseudo- reduction, 248; fertilization of Cyclops, 193; independence of germnuclei, 208, 209; reduction in copepods, 249» 251 ; early history of germ-nuclei, 273; reduction in selachians, 257; history of germinal vesicle, 338.

Riige, amitosis, 117.

Ryder, staining-reactions, 175.

SabaschnikofT, tetrads, 256.

Sabatier, amitosis, 116.

Sachs, energid, 19, 30; laws of cell-division, 362; cell-division and growth, 393; development, 427.

St. George, I-a Valette, spermatozoon, 10, 134; spermatogenesis (terminology), 161.

Sala, polyspermy, 199.

Sargant, reduction in plants, 267.

Schafcr, protoplasm, 29.

Scharff, budding of nucleus, 155.

Schaudinn, mitosis in Protozoa, 92, 94, 102; polar bodies, 278.

Schewiakoff, mitosis in Euglypha, 91.

Schimper, plastids, 290.

Schleicher, karyokinesis, 64.

Schleiden, cell-theory, I; cell-division, 9; nature of cells, 17; fertilization, 218.

Schloter, granules, 38, 303.

Schmitz, plastids, 290; conjugation, 216.

Schneider, discovery of mitosis, 64.

Schottlander, multipolar mitosis, 99.

Schultze, M., cells, 1, 19; protoplasm, 20.

Schultze, O., mitosis, 318; gravitation-experiments, 422; double embryos, 422.

Schwann, cell-theory, I; the egg a cell, 8; origin of cells, 9; nature of cells, 17; organization's; adaptation, 433.

Schwarz, protoplasm, 42 ; linin, 33; chemistry of nucleus, 41 ; nuclei of growing cells,

340. Schweigger-Seidel, spermatozoon, 9, 134. Sedgwick, cell- bridges, 60. Seeliger, egg-fragments, 353; egg-axis, 379. Selenka, double spermatozoa, 142. Shaw, spermatozoids, 175. Siedlecki, polar bodies, 280. Sobotta, fertilization, 185, 211. Solger, pigment-cells, 102; attraction-sphere,

5 1 Spallanzani, spermatozoa, 9; regeneration,




Spencer, physiological units, 289; development, tyi.

Stauffacher, egg-cent rosome, 125.

Stevens, fertilization, 217.

Strasburger, 1, 7; cytoplasm, 20; Kdrnerplasma, 41; centrosphere, 68, 356, 324; membranes, 55; origin of amphiaster, 82; multipolar mitoses, 99; theory of mitosis, 105, no; spermatozoids, 173; kinoplasm, 27, 82, 322; staining-reactions of germnuclei, 220; fertilization in plants, 216, 219, 221; reduction, 265, 269; theory of maturation, 275; organization, 289; inheritance, 7, 182, 35 1; action of nucleus, 426.

Zur Strassen, giant-embryos, 296; germcells, 148.

Van der Stricht, spindle, 79; amitosis, 116; fertilization, 210; reduction, 259; centrosome and sphere, 312, 325.

Strobe, multipolar mitoses, 99.

Stuhlmann, yolk-nucleus, 156.

Suzuki, spermatogenesis, 168.

Swingle, mitosis, 82.

Tangl, cell-bridges, 59.

Thiersch and Boll, theory of growth, 392.

Townsend, cell-bridges, 61, 346.

Treat, sex, 145.

Treviranus, variation, 179.

Unna, protoplasm, 27.

Ussow, micropyle, 133; deutoplasm, 153.

Yejdovsky, centrosome, 76; fertilization in Rhynchelmis % 192, 194; metamerism in annelids, 390.

Yerworn, cell-physiology, 6; regeneration in Protozoa , 344; inheritance, 359, 431.

Yirchow, I; cell-division, 10, 63; protoplasm, 25: cell-state, 5S.

m t

De Vries, organization, pangens, 291, 327, 406; tonoplasts, 53; plasties, 229; chromatin, 431 ; development, 404.

Waldeyer, nucleus, 3S; cytoplasm, 41 ; cellmembrane, 54. Walter, frog-e\periments, 419. Watase, theory of mitosis, 106; stain ing


reactions of germ-nuclei, 176; nucleus and cytoplasm, 292; asters, 305; theory of cent rosome, 315; astral rays, 321 ; cleavage of squid, 381 ; promorphology of ovum, 3S3.386.

Webber, spermatozoids, 144, 173; fertilization, 221.

Weismann, inheritance, 12; cell -organization, biophores, 291 ; somatic and germ cells, 122; amphimixis, 179; maturation, 243-246; constitution of the germ-plasm. 245; parthenogenesis, 281 ; theory of development, 404, 407, 432.

Went, vacuoles, 53.

Wheeler, amitosis, 115; insect-egg, 132; egg of Myzostoma, 151 ; fertilization in Mytostoma^ 208; bflateralitv of ovum, 3S5.

Whitman, on Harvey, 7; polar rings, 202: cell-division and growth, 393; polarity, 384; theory of development, 400, 416.

Wiesner, cell-organization, 290, 291.

Wilcox, sperm-centrosome, 165; reduction*

257. Will, chromatin-elimination, 135.

Wilson, protoplasm, 27, 44; mitosis, 106: fertilization in sea-urchin, 187, 212; paths of germ-nuclei, 202; origin of linin, 303: astral rays, 28; centrosphere and centr**some, 314; dispermy, 355; rudimentary cells, 372; pressure-experiments, 41 1: experiments on Amphioxus? 410; theory of development, 415.

Von Wittich, yolk -nucleus, 155.

Wolff, C. F., epigenesis, 8.

Wolff, G., regeneration of lens, 433.

Wolters, polar bodies in gregarines, 27S.

Yung, sex, 144.

Zacharias, E., nucleoli, 34; of meristem. 37; staining-reactions, 176; nuclein in growing-cells, 340.

Zacharias, O., amoeboid spermatozoa. 142.

Ziegler, artificial mitotic figure, 10S; amitosis, 117; sphere, 324.

Zimmerman, pigment-cells, 102; centrosome,


Zoja, independence of chromosomes, 209; isolated blastoiueres, 410.


AcanthoeysttSy 94, 304, 306.

Achromatic figure (see Amphiaster), 69;

varieties of, 78; nature, 316. Achromatium, 39. ActinophrySy 92, 278. Actinosph&rium, mitosis, 90, 94; reduction,

278; regeneration, 342. s&quorta, metanucleus, 128. Albugo, 217. Albumin, 331. Allium, 83, 253, 267. Allolobophora, teloblasts, 374. Alveoli, 25. Amitosis, 114; biological significance, 116;

in sex-cells, 285. Amaba, 5; mitosis, 91 ; experiments on,

343Amphiaster, 68; asymmetry of, 70, 373;

origin, 72, 74, 316; in amitosis, 116; in fertilization, 187, 213; nature, 316; position, 375.

Amphibia, spermatozoa, 140; sex, 145.

Ampkioxus, fertilization, 210; polar body, 236, 277; cleavage, 370; dwarf larvae, 389, 410; double embryos, 410.

Amphipyrenin, 41.

Amphiuma, 167, 261.

Amyloplasts, 53; in plant-ovum, 133.

Anaphases, 70; in sea-urchin egg, 106.

Anasa % sperm-formation, 165, 271; reduction, 272.

Ancylus, 368.

Aniloera, gland-cells, nuclei, 36; amitosis, 116.

Anodonla, ciliated cells, 43, 357.

Antipodal cone, 101.

A plus, 281.

Arbaa'a, 192, 21 5, 307.

Archoplasm, 69; in developing spermatozoa, 171; nature of, 318.

Archosome, 52.

Argonautiiy micropyle, 133.

Aricia, rudimentary cells, 372.

Arion, spindle, 81 ; germ-nuclei, 207.

Arisama, 269.

Artemia, chromosomes, 89; parthenogenetic maturation, 281.

Artifacts, in protoplasm, 42.

Ascaris, chromosomes, 87, 301 ; mitosis, 80, ioi; primordial germ-cells, 146; fertilization, 182, 211; polyspermy, 199; polar bodies, 238; spermatogenesis, 241, 253; individuality of chromosomes, 295; intranuclear centrosome, 304; centrosome, 311; attraction-sphere, 323; supernumerary centrosome, 355.

Aster, 68; asymmetry, 70; structure and functions, 101; in amitosis, 116; in fertilization, 187, 213; nature of, 316; finer structure, 326; relative size, 70, 373.

Asttrias, spermatozoa, 176; sperm-aster, 187; fertilization, 192, 210.

Astrocentre, 324.

Astrosphere, 324.

Attraction-cone, 198.

Attraction-sphere, 51, 72; in amitosis, 115; of the ovum, 125; of the spermatid, 163; in resting cells, 323; nature of, 323.

Axial filament, 136; origin of, 165.

Axis, of the cell, 55 ; of the nucleus, 36, 294; of the ovum, 378, 386.

Axolotl, fertilization, 192.

Bacteria, nuclei, 31, 39.

Basichromatin, 38; staining-reactions, 338.

Bioblast, 290.

Biogen, 291.

Biophore, 245, 291.

Birds, blood-cells, 57; spermatozoa, 138; young ova, 155.

Blastomeres, displacement of, 366; individual history, 378; prospective value, 415; rhythm of division, 366, 389; development of single, 409, 418; in normal development, 423.

BUnnius, pigment-cells, 103.

Blepharoplastoids, 175.

Blepharoplasts, 173, 221.

Branchipusy yolk, 153; sperm-aster, 192; reduction, 256.




Calanus, tetrads, 25a

CalopUnus, 165, 257.

Cambium, 376.

Cancer-cells, mitosis, 98.

CanthocamptuSj reduction, 251 ; ovarian eggs, 273.

Cell, in general, 4; origin, 9; name, 17; general sketch, 19; polarity of, 55; as a structural unit, 58; structural basis, 23, 293; physiology and chemistry, 330; size and numerical relations, 389; in inheritance, 9, 430; differentiation of, 413, 426; independence of, 427.

Cell-bridges, 59.

Cell-division (see Mitosis, Amitosis), general significance, 10, 63; general account, 65; types, 64; Remak's scheme, 63; indirect, 65; direct, 114; cyclical character, 178, 223; equal and reducing or qualitative, 405; relation to development, 388, 405, 410, 427; Sachs's laws, 362; rhythm, 366, 389; unequal, 370; of teloblasts, 371 ; energy of, 388; relation to metamerism, 390; causes, 391; relation to growth, 388; and differentiation, 427.

Cell-membrane, 53.

Cell-organization, 289.

Cell-organs, 52; nature of, 291 ; temporary and permanent, 292.

Cell-plate, 71.

Cell-state, 58.

Cell-theory, general sketch, I-14.

Central spindle, 70, 78.

Centrodesmus, 79, 315.

Centrodeutoplasm, 163, 324.

Centroplasm, 324.

Centrosome, 22; general sketch, 50, 304; position, 55; in mitosis, 74; a permanent organ, 74; dynamic centre, 76; historical origin, 315; functions, 101, 354; in amitosis, 115; of the ovum, 125; of the spermatozoon, 137, 165-170; in fertiliza- ' tion, 100, 208; degeneration of, 186, 213; | continuity, 74, 77, 194, 214, 321 ; nature, 1 304; intra-nuclear, 304; supernumerary,

355Centrosphere, 68, 85; nature of, 324.

CeratiutHy 91.

Ct-ra/ozd/f/Kjy reduction, 275.

Cerebratidus, 193, 194,213, 306,307,321,325.

CerianthttSy regeneration in, 392.

Chictopttrus, spindle, 81, 84; fertilization,

192; sperm-centrosome, 213; centrosomes

de novo, 306; cell-division, 391. Chara, spermatozoids, 143.

Chilomonas, 32, 40, 192.

Chironomusj spireme-nuclei, 36.

Chorion, 132.

Chromatic figure, 69; origin, 72; varieties, 86; in fertilization, 181, 204.

Chromatin, 33; in meristem, 37; in mitosis, 65, 86; in cancer-cells, 98; of the eggnucleus, 126; elimination of, in cleavage, 147,426; in oogenesis, 233, 276; staining . reactions, 334-340; morphological organization, 37, 245, 294; chemical nature, 332, 404; relations to linin, 302 ; physiological changes, 338; as the idioplasm, 352; in development, 405, 425, 431.

Chromatin-granules, 37; in mitosis, 112; in reduction, 248; general significance, 301304; relations to linin, 302.

Chromatophore, 53; in the ovum, 133; in fertilization, 229.

Chromiole, 302.

Chromomere (see Chromatin-granule), 37, 301.

Chromoplast, 53.

Chromosomes, 67, 70, 86, 112; number of, 67, 206; bivalent and plurivalent, S7; division, 112; of the primordial germcell, 148; in fertilization, 182, 204; independence in fertilization, 204; reduction, 238, 243, 248; in early germ-nuclei, 273; conjugation of, 257; in parthenogenesis, 281 ; individuality of, 294; composition of, 301; chemistry, 334, 336; history in germinal vesicle, 338 ; in dwarf larvae, 296.

Ciliated cells, 44, 57.

Ciona, egg-axis, 379.

Clavelina, cleavage, 369, 381.

Cleavage, in general, 10 ; geometrical relations, 362; Sachs's rules, 362; Hertwig's rules, 364; modifications of, 366; spiral, 368; reversal of, 368; unequal, 370; under pressure, 375,41 1 ; promorphology of, 37S: bilateral, 381 ; rhythm, 366, 388; mosaic theory, 399, 423; half cleavage, 410.

Cleavage-nucleus, 204.

Cleavage-planes, 362; axial relations, 378.

Ciepsiiie, nephridial cell, 45; polar rings, 202 : cleavage, 370.

Ciosterinm, conjugation and reduction, 280.

Cockroach, amitosis, 115; orientation of egg,

384. Ccrlenterates, germ-cells, 146; regeneration,

392, 393. 430Conjugation, in unicellular animals, 222; unicellular plants, 228, 280; physiological meaning, 178, 223.



Contractility, theory of mitosis, ioo; inadequacy, 106.

Copepods, reduction, 251.

Corixa, ovum, 383.

Corpuscule central, 310, 314.

Crcpidula, fertilization, 210; dwarfs and giants, 389; cleavage, 323, 423.

Cross-furrow, 368. Crustacea, spermatozoa, 142.

Ctenophores, experiments on eggs, 418.

Cucurbita, 346.

Cuticular, 54.

Cyanophyceae, nucleus, 31, 39.

Cycads, spermatozoids, 144, 173; fertilization, 218, 221.

tyc/ops, o\'3i, 128; primordial germ-cells, 148; fertilization, 188; reduction, 251; attraction-sphere, 325; axial relations, 385.

Cytoplasm, 21, 41, 293, 303; of the ovum, 130; of the spermatozoon, 134; morphological relations to nucleus, 302; to archoplasm, 316, 319; chemical relations to nucleus, 333-341; physiological relations to nucleus, 341 ; in inheritance, 352-354, 359; in development, 398,421 ; origin, 431.

Cytosome, 322.

Dendrobana, metamerism, 390.

Determinants, 245.

Deutoplasm, 131 ; deposit, 153; effect on cleavage, 366, 371; rearrangement by gravity, 422.

Development, I-12; and cell-division, 388; mosaic theory, 399, 421 ; theory of Nagcli, 402; Roux-Weismann theory, 404; of single blastomeres, 399, 409, 418; of eggfragments, 296, 353, 419; De Vries's theory, 413; Hertwig's theory, 415, 432; Driesch's theory, 394, 415; partial, 409, 419; half and whole, 419; nature of, 413; external conditions, 428; and metabolism, 430; unknown factor, 431 ; rhythm, 432; adaptive character, 433.

Diaptomus, 250.

Diatoms, mitosis, 92; centrosome, 51.

Diaulula, 79, 314.

Diemyctylus, yolk, 153; yolk-nuclei, 156.

Differentiation, 361 ; theory of De Vries, 404; of Weismann, 405; nature and causes, 413; of the nuclear substance, 425 ; and cell-division, 427.

Dipsacus, 346.

Dispermy, 355.

Double embryos, 410, 422.

Drosera, 350.

Dwarfs, formation of, 353, 410, 422; size of cells, 389.

Dyads (Zweiergruppen), 239, 24 1; in parthenogenesis, 284.

Dyaster, 70.

Dycyemids, centrosome, 51.

Dytiscus, ovarian eggs, 153, 349.

Earthworm, ova, 152; spermatozoon, 165; yolk-nucleus, 154; polar rings, 156, 202; spermatogenesis, 257; teloblasts, 374.

Echinoderms, protoplasm, 28, 44, 293; spermatozoa, 137; fertilization, 188, 212; polyspermy, 194, 198; dwarf larvae, 353, 410; half cleavage, 410; eggs under pressure, 41 1 ; modified larvae, 428.

Echinus, fertilization, 210; centrosome, 314 ; dwarf larvae, 353; number of cells, 389.

Ectosphere, 324.

Egg-axis, 378; promorphological significance, 379; determination, 386; alteration, of, 422.

Egg- fragments, fertilization, 194; development, 352.

Elasmobranchs, spermatozoon, 140, 167, 169; germinal vesicle, 245, 273; reduction, 257.

Embryo-sac, 218, 263.

Enchylema, 23.

End-knob, 136.

Endoplasm, 41.

End-piece, 140.

End-plate, 91.

Energid, 19, 30.

Entosphere, 324.

Envelopes, of the egg, 132.

Epigenesis, 8, 432.

Equatorial plate, 68.

Equisetum, mitosis, 85.

Ergasto plasm, 322.

Erysiphe, mitosis, 82.

Euchictciy tetrads, 250.

Euglena, mitosis, 91, 315.

Euglypha % mitosis, 89, 95.

Evolution (preformation), 8, 399, 432.

Evolution, theory of, 2, 8.

Exoplasm, 41.

Fertilization, general aspect, 9; physiological meaning, 180; general sketch, 180; Ascaris, 182; mouse, 185; sea-urchin, 188; Nereis, 188; Cyclops, 188; Thalassema, Chatopterus, 193, 195; pathological, 198; partial, 190, 194; of Afyzostoma, 196, 208; in plants, 215; egg- fragments, 194; Boveri's theory, 192, 211.



Fishes, pigment-cells, 102; periblast-nuclei, 117; spermatozoa, 137; young ova, 116; single blastomeres, 410.

Flagellates, diffused nuclei, 39.

Follicle, of the egg, 150.

Forficula, nurse-cells, 15 1.

Fragmentation, 64.

Fritillaria, spireme, 112; fertilization, 219.

Frog, tetrads, 259; egg-axis, 378; first cleavage-plane, 380; Roux's puncture experiment, 399; post-generation, 409; pressureexperiments, 410; effect of gravity on the egg, 422; development of single blastomeres, 399, 408, 422; double embryos, 422.

Fucus, 143, 217, 221.

Ganglion-cell, 48; centrosome in, 51, 314.

Gemmae, 291.

Gemmules, 12, 291.

Genoblasts, 243.

Gtophilus* deutoplasm, 154, 158; yolk-nucleus, 156.

Germ, 7, 396.

Germ-cells, general, 8, 9; detailed account, 122; of plants, 133, 142; origin, 144;. growth and differentiation, 150; union, 196; results of union, 200; maturation, 233; early history of nuclei, 272.

Germinal localization, theory of, 397.

Germinal spot, 124.

Germinal vesicle, 124, 125; early history, 273; movements, 349; position, 387.

Germ-nuclei, of the ovum, 125; of the spermatozoon, 135; of plants, 216; staining-reactions, 175; in fertilization, 182, 188; equivalence, 182, 205; paths, 202; movements, 204; union, 204; independence, 204, 299; in Infusoria, 224; early history, 272.

Giant-cells, 31; microcentrum, 314.

Gingko, 173.

Globulin, 331, 333.

Granules (see Microsomes), of Altmann, 290; nuclear, 37, 303; chromophilic, 23, 48; in general, 289.

Gravity, effect on the egg, 1 31, 422.

Gregarines, mitosis, 89; polar body, 278.

Ground-substance, of protoplasm, 23; of nucleus, 36.

Growth, and cell-division, 58, 388.

Gryllotalpa, reduction, 249.

Guinea-pig, spermatogenesis, 170; maturation, 277.

Heliozoa, 92, 103.

Helix, 163, 168, 259.

HcmcrocalliSy 306.

Hcterocope, tetrads, 250.

Heterokinesis, 406.

Histon, 334, 336.

Homceokinesis, 406.

Hydrophilusy orientation of egg, 384.

Id, in reduction, 245; in inheritance, 406.

Idant, 245.

Idioblast, 291.

Idioplasm, theory of, 401 ; as chromatin, 403; action of, 406, 414, 431, 432.

Idiosome, 291.

Idiozome, 163, 165, 324.

Ilyanassa, partial development, 419.

Infusoria, nuclei, 31, 224; mitosis, 90; conjugation, 223; reduction, 277.

Inheritance, of acquired characters, 12, 433 J Weismann's theory, 12; through the nucleus, 351-354 ; and metabolism,

430Inotagmata, 291.

Insect-eggs, 132, 386.

Interzonal fibres, 70.

Iris, 267.

Isopods, metamerism, 390.

Isotropy, of the egg, 384, 417.

Karyokinesis (see Mitosis), 64. Karyokinetic figure (see Mitotic Figure),

69. Karyolymph, 36. Karyoplasm, 21. Karyosome, 34. Kinoplasm (archoplasm), 54, 77, 82, 173,


Lanthanin, 38.

Lepidoptera, sex, 144.

Leucocytes, structure, 102; division, 117; centrosome, 309; attraction-sphere, 326.

Leucoplasts, of plant-ovum, 133.

Liliuitiy mitosis, 83; spireme, 1 12; fertilization, 219; reduction, 265-271.

Lima.Xy germ-nuclei, 204.

Li m 14 1 us y 158.

Linin, 32; relations to cytoreticulum and chromatin, 302.

Li pa r is t 281.

Locus/ay orientation of egg, 384.

LoligOy spindle, 81 ; cleavage, 381.

LumbricttSy yolk-nucleus, 157; reduction,

2 57



Macrobdella, 305.

Macrogamete, 226.

Macromeres, 371.

Mammals, spermatozoa, 139, 169; young ova, 155.

Mantle-fibres, 78, 105.

Marsilia, 175.

Maturation (see Reduction), 234; theoretical significance, 243; of parthenogenetic eggs, 280; nucleus in, 353.

Medusae, dwarf embryos, 410.

Meristem, nuclei of, 340.

Metamerism, 390.

Metanucleus, 128.

Metaphase, 69.

Metaplasm, 19.

Micellae, 291.

Microcentrum, 31 1, 315, 324.

Microgamete, 226.

Micromeres, 371.

Micropyle, 124, 133.

Microsomes, 23; of the egg-cytoplasm, 131 ; nature of, 289, 290, 293 ; of the astral systems, 318, 326; of the nucleus, 301, 303; relation to centrosome, 315; stainingreactions, 337.

Microsphere, 324.

Microzyma, 291.

Mid- body, 71, 78.

Middle-piece, 135, 139; origin, 1 61, 165170; in fertilization, 187, 212.

Mitosis, 64; general outline, 65; modifications of, 77; heterotypical, 86; in unicellular forms, 87; pathological, 88; multipolar, 97; mechanism of, 100; physiological significance, 351 ; Roux-Weismann conception of, 245, 406.

Mitosome, 165.

Mitotic figure (see Mitosis, Spindle), 69; origin, 72; varieties, 78.

Molgula, 158.

Mouse, fertilization, 185, 193.

iVusca, ovum, 142.

Myriapods, spermatozoa, 142; yolk-nucleus, 156.

Afyzostoma, fertilization, 196, 208.

A r aias, 266.

Nebenkern, pancreas-cells, 44; of spermatid,

163, 165. Nebenkorper, 164, 165. Necturus, pancreas-cells, 44. Nematodes, germ-nuclei, 184. Nereis, asters, 49; perivitelline layer, 131 ;

ovum, 129; deutoplasm, 131; fertilization,

2 I

191; attraction-sphere and centrosome, 325; cleavage, 366, 369; pressure-experiments on, 411.

Nerve-cell, 48.

Net-knot, 34.

Noctiluai, mitosis, 93; flagellum, 171 ; conjugation, 227; sphere, 319.

Nuclear stains, 335.

Nuclein, 33, 332; staining-reactions, 334; physiological significance, 340.

Nuclein-bases, 331.

Nucleinic acid, 33, 332-334; staining-reactions, 334 ; physiological significance,


Nucleo-albumin, 331, 334.

Nucleo-proteid, 331, 334.

Nucleolus, 33; in mitosis, 67; of the ovum, 126; physiological meaning, 128.

Nucleoplasm, 21.

Nucleus, general structure and functions, 31; finer structure, 37; polarity, 36, 294; chemistry, 41; in mitosis, 65; of the ovum, 125; of the spermatozoon, 135, 137; relation to cytoplasm, 302; morphological composition, 294; in organic synthesis, 340, 430; physiology, 341; position and • movements, 346; in fertilization, 181,352; in maturation, 353; in later development, 425; in metabolism and inheritance, 430; in inheritance and development, 341, 358, 405, 425, 431 ; control of the cell, 426.

Nurse-cells, 151.

(Edigonium, fertilization, 181; membrane,


Onoclea, 175.

Oocyte, 236.

Oogenesis, 234, 236.

Oogonium, 236.

Oosphere, 133.

Ophryotrocha, amitosis, 1 15; nurse-cells, 151; fertilization, 189, 193; tetrads, 258.

Opossum, spermatozoa, 142.

Organization, 289, 291 ; of the nucleus, 294, 301; of the egg, 397, 433.

Origin of species, 3.

Osmunda, reduction, 275.

Ovary, 123; of Canthocamptus, 273.

Ovum, in general, 8, 9; detailed account, 124; nucleus, 125; cytoplasm, 130; envelopes, 132; of plants, 133; origin and growth, 150; fertilization, 178; effects of spermatozoon upon, 201 ; maturation, 236; parthenogenetic, 280; promorphology* 378; hilaterality, 382.



Oxychromatin, 38, 303; staining-reactions,

337Oxydation-ferments, 351.

Oxytricha, 342.

Oyster, germ-nuclei, staining-reactions, 175.

Pallavicinia, reduction, 275.

Paludina, dimorphic spermatozoa, 141.

Pangenesis, 12, 290, 431.

Pangens, 291.

Parachromatin, 41.

Paralinin, 41.

Paramaba, mitosis, 94, 315.

Parametrium, mitosis, 91 ; conjugation, 224; reduction, 277.

Paranucleus, 163.

Parthenogenesis, theories of, 281; polar bodies in, 280.

Pellicle, 54.

Pentatoma, 271.

Pctromyzon, fertilization, 192, 212.

Phallus ia, fertilization, 193, 212.

Physa % fertilization, 193, 210, 212; reversed cleavage, 368.

Physiological units, 289.

PiertSy spinning-gland, 37.

Pigment-cells, 102.

Pilularia, fertilization, 216.

Pinus, reduction, 275.

Planaria, regeneration, 394.

Plant-cells, plastids, 52; membranes, 54; mitosis, 82; cleavage-planes, 363.

Plasma-stains, 335.

Plasmocyte, 52.

Plasmosome, 34.

Plasome, 291.

Plastids, 52; of the ovum, 133; of the spermatozoid, 143; conjugation of, 229.

Plastidule, 291.

Plastin, 41, 331.

Pleurophyllidia, 78, 94.

Podophyllum, 267.

Polar bodies, 181; nature and mode of formation, 235-240; division, 236; in parthenogenesis, 281.

Polar rings, 1 56, 202.

Polarity, of the nucleus, 36; of the cell, 55; of the ovum, 378; determination of, 382.

Pole-plates, 91.

Pollen-grains, formation, 263-265.

Pollen-tube, 218.

Polyclades, cleavage, 416.

PolychceruSy 276, 325.

Polygordim* cleavage, 368.

Polyspermy, 198; prevention of, 199.

Pofystomella % regeneration, 344.

Polyzonium, 159.

Porcellio, amitosis, 116.

Predelineation, 398.

Preformation (see Evolution).

Pressure, experiments, 375, 410.

Principal cone, 101.

Pristiurus, 338.

Promorphology (see Cleavage, Ovum).

Pronuclei, 202.

Prophase, 65.

Prostheceraus, 213, 235, 256, 259, 306.

Prostkiostomum, 212.

Protamin, 334.

Proteids, 331.

Prothallium, 264; chromosomes in, 275.

Protoplasm, 4, 5, 17, 19; structure, 23,42,

293; chemistry, 331. Protoplast (see Plastid). Pseudo-alveolar structure, 50. Pseudo-reduction, 248. Pteris, 253.

PUrotrachea, germ-nuclei, 186, 205. Ptychoptera, spireme-nuclei, 35. Pyg<rra t 165. Pyrenin, 41. Pyrenoid, 133. Pyrrhocoris, 165, 248.

Quadrille of centres, 210.

Rat, spermatogenesis, 170.

Reduction, general outline, 234; parallel between the two sexes, 241 ; theoretical significance, 243; detailed account. 246; in plants, 263; Strasburger's theory of, 275; in unicellular forms, 277; by conjugation, 257; modes contrasted, 247.

Regeneration, Weismann's theory, 406; in frog-embryo, 409; nature of, 425, 427; in coelenterates, 430; of lens, 433.

Rejuvenescence, 179, 224.

Renilla, ovum, 132.

Rhabdonema, amitosis, 1 1 5.

l\hynchelmis> fertilization, 192, 193, 212; cleavage, 370.

Rotifers, sex, 145.

Sagitta, number of chromosomes, 184; primordial germ-cells, 146; germ-nuclei, 184; spermaster, 191.

Salamander, epidermis, 3; spermatogonia, 20; mitosis in, 71, 78; pathological mitosis, 98; leucocytes, 1 02; spermatozoa, 140 ; maturation, 259.



Sargus, pigment-cells, 103. Scyllium, 263.

Segmentation (see Cleavage). Selaginetla, spermatozoids, 197. Senescence, 179. Sepia, spindle, 81. Sertoli-cells, 284.

Sex, 9; determination of, 144; Minot's theory of, 243. Siphonophores, amitosis, 117. Soma, 13. Somacule, 291. Somatic cells, 122; number of chromosomes,

233Spermary, 123.

Spermatid, 161, 1 63; development into spermatozoon, 164.

Spermatocyte, 161, 241.

Spermatogenesis (see Reduction), 234; general outline, parallel with oogenesis, 241.

Spermatogonium, 161, 241.

Spermatozeugma, 142.

Spermatozoid, structure and origin, 142, 172; in fertilization, 217, 221.

Spermatozoon, discovery, 9; structure, 134; essential parts, 135; giant, 141 ; double, 142; unusual forms, 142; of plants, 142; formation, 160; in fertilization, 1 81, 192; entrance into ovum, 197.

Sperm-centrosome, 135, 1 64-1 71; in fertilization, 192, 211-215, 22I>

Sperm-nucleus, 135; origin, 164-171; in fertilization, 182, 190; rotation, 188; path in the egg, 202; in inheritance, 353; chemistry, 334.

Sphtrrechinus, fertilization, 193, 210; number of cells, 389; hybrids, 353; regcnera• tion, 393.

Spindle (see Amphiaster, Central Spindle) , 68 ; origin, 72, 79,82; in Protozoa, 90; conjugation of, 227; nature of, 316; position, 375.

Spireme, 65.

Spirochona, mitosis, 90.

Spirogyra, nucleolus, 67 ; amitosis, 1 19 ; conjugation, 229; reduction, 280.

Spongioplasin, 25.

Spontaneous generation, 7.

Stem-cells, 148.

Stentor, regeneration, 342.

Stylonychia, senescence, 224.

Stypocaulon, mitosis, 82.

Surirella, 94.

Symbiosis, 53, 292.

Synapta, cleavage, 364.

Syncytium, 59.

Teloblasts, 371, 390.

Telophase, 71.

Tetrads (Vierergnippen), 238; origin, 246; in A scar is, 241, 253; in arthropods, 248; ring-shaped, 248; in amphibia, 259; origin by conjugation, 257; formulas for,

247. Teiramitus, 40, 92.

Thalassema, spindle, 81 ; fertilization, 193, 194, 213; reduction, 259, 263; centrosome, 321 ; attraction-sphere, 325.

Thalassicolla, experiments on, 344.

Thysanozodn, 212, 259, 326.

Tonoplast, 53.

Toxopneustes, cleavage, 10; mitosis, 107; ovum, 126; spermatozoon, 134; fertilization, 188; paths of germ-nuclei, 202; polar bodies, 114; double cleavage, 355.

Trachelocerca, diffused nuclei, 40.

Trilli unit 269.

Triton, 1 40, 212, 263, 277.

Trophoplasm, 322, 401.

Tubularia, regeneration, 430.

Tunicates, egg-axis, 379; cleavage, 381.

Unicellular organisms, 5; mitosis, 88; conjugation, 222; reduction, 277; experiments on, 342.

Unio, ceiitrosome and aster, 314; cleavage.

381. Urostyla, 40.

Vacuole, 50, 53.

Vanessa, ovarian e^, 153.

Variations, 1 1 ; origin of, 433.

Vaucheria, membrane, 348.

Vitalism, 394, 417.

Vitelline membrane, 132; of egg-fragments,

132; formation of, 198; function, 199. Volvox, germ-cells, 133. Vorticella, conjugation, 226.

Xiphidium, 271.

Yellow cells (of Radiolaria), 53. Yolk (see Deutoplasm), 152. Yolk -nucleus, 155. Yolk -plates, 131.

Zamia, 173, 221. Zirpfura, 259, 263. Zwischenkorper (mid-body), 71. Zygnema, membrane, 346. Zygospore, 228.



Columbia University Biological Series.



Da Costa Professor of Zoology in Columbia Cnirtrsity.

This series is founded upon a course of popular University lectures given during the winter of 1892-3, in connection with the opening of the new department of Biology in Columbia College. The lectures are in a measure consecutive in character, illustrating phases in the discovery and application of the theory of Evolution. Thus the first course outlined the development of the Descent theory; the second, the application of this theory to the problem of the ancestry of the Vertebrates, largely based upon embryological data; the third, the application of the Descent theory to the interpretation of the structure and phylogeny of the Fishes or lowest Vertebrates, chiefly based upon comparative anatomy ; the fourth, upon the problems of individual development and Inheritance, chiefly based upon the structure and functions of the cell.

Since their original delivery the lectures have been carefully rewritten and illustrated so as to adapt them to the use of College and University students and of general readers. The volumes as at present arranged for include:

I. From the Greeks to Darwin. By Henry Fairfield


II. Ampliioxus and the Ancestry of the Vertebrates.

Bv Arthur Willey. III. Fishes, Living and Fossil. By Bashford Dean. IV. The Cell in Development and Inheritance. By

Edmund B. Wilson.

V. The Foundations of Zoology. By William Keith Brooks.







Da Costa Prufe*nor of Zoology in Columbia University. 8vo. Cloth. $2.00, net.

This opening volume, " From the Greeks to Darwin," is an outline of the development from the earliest times of the idea of the origin of life by evolution. It brings together in a continuous treatment the progress of this idea from the Greek philosopher Thales (640 B.C.) to Darwin and Wallace. It is based partly upon critical studies of the original authorities, partly upon the studies of Zeller, Perrier, Quatrefages, Martin, and other writers less known to English readers.

This history differs from the outlines which have been previously published, in attempting to establish a complete continuity of thought in the growth of the various elements in the Evolution idea, and especially in the more critical and exact study of the pre-Darwinian writers, such as Buffon, Goethe, Erasmus Darwin, Treviranus, Lamarck, and St. Hilaire, about whose actual share in the establishment of the Evolution theory vague ideas are still current.


I. The Anticipation and Interpretation of Nature. II. Among the Greeks.

III. The Theologians and Natural Philosophers.

IV. The Evolutionists of the Eighteenth Century. V. From Lamarck to 8t. Hilaire.

VI. The First Half-century and Darwin.

In the opening chapter the elements and environment of the Evolution idea are discussed, and in the second chapter the remarkable parallelism between the growth of this idea in Greece and in modern times is pointed out. In the succeeding chapters the various periods of European thought on the subject are covered, concluding with the first half of the present century, especially with the development of the Evolution idea in the mind of Darwin.




Tutor in Biology, Columbia Vnirer»ity ; Balfour Student of the,

Unirertity of Cambridge.

8vo. Cloth. $2.50, net.

The purpose of this volume is to consider the problem of the ancestry of the Vertebrates from the standpoint of the anatomy and development of Amphioxus and other members of the group Protochordata. The work opens with an Introduction, in which is given a brief historical sketch of the speculations of the celebrated anatomists and embryologists, from Etienne Geoffroy St. Hilaire down to our own aay, upon this problem. The remainder of the first and the whole of tne second chapter is devoted to a detailed account of the anatomy of Amphioxus as compared with that of higher Vertebrates. The third chapter deals with the embryonic and larval development of Amphioxus, while the fourth deals more briefly with the anatomy, embryology, and relationships of the Ascidians; then the other allied forms, Balanoglossus, Cephalodiscus, are described.

The work concludes with a series of discussions touching the problem proposed in the Introduction, in which it is attempted to define certain general principles of Evolution by which the descent of the Vertebrates from Invertebrate ancestors may be supposed to have taken place.

The work contains an extensive bibliography, full notes, and 135 illustrations.



Chapter I. Anatomy of Amphioxus. II. Ditto.

III. Development of Amphioxus.

IV. The Ascidians.

V. The Protochordata in their Relation to the Problem of Vertebrate Descent.