Book - Outline of Comparative Embryology 1-1

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Richards A Outline of Comparative Embryology. (1931)
1931 Richards: Part One General Embryology 1 Historical Development of Embryology | 2 The Germ-Cell Cycle | 3 Egg and Cleavage Types | 4 Holoblastic Types of Cleavage | 5 Meroblastic Types of Cleavage | 6 Types of Blastulae | 7 Endoderm Formation | 8 Mesoderm Formation | 9 Types of Invertebrate Larvae | 10 Formation of the Mammalian Embryo | 11 Egg and Embryonic Membranes | Part Two Embryological Problems 1 The Origin And Development Of Germ Cells | 2 Germ-Layer Theory | 3 The Recapitulation Theory | 4 Asexual Reproduction | 5 Parthenogenesis | 6 Paedogenesis And Neoteny | 7 Polyembryony | 8 The Determination Problem | 9 Ecological Control Of Invertebrate Larval Types

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This historic 1931 embryology textbook by Richards was designed as an introduction to the topic. Currently only the text has been made available online, figures will be added at a later date. My thanks to the Internet Archive for making the original scanned book available.
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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Part One General Embryology

Historical Development of Embryology

The science of embryology is scarcely a century old, dating from the work of Pander (1817) and von Baer (1827) whose investigations into developmental phenomena were more accurate than those of the earlier students and who were the first to give systematic form to the subject; but interest in and curiosity as to the events of the pre—natal period in animals or of the life and growth of an embryo, especially of the chick before hatching, goes back to the ancients, as evidenced by the contributions by Aristotle and Galen among the Greeks. Aristotle was the author of three works of great zoological importance, in one of which, “De Generatione Animalium,” are given the results of his observations on the reproduction of various forms of animals as well as a description of the progressive stages in the development of an incubated egg. These observations were made directly upon the egg without the aid of lenses, and of course were very incomplete. The advance of embryological knowledge waited for the application of the lens to the study of life forms and processes which began seine four hundred years ago. With the invention of the microscope the subject wen fresh impetus until it became one of the major biological sciences when supported by exact cell studies in the last century.

Following Loey,* we may divide the progress during this time into periods as follows: (1) the period of Harvey and Malpighi; (2) the period of Wolff; (3) the period of von Baer; (4) the period from von Baer to Balfour; (5) the period of Balfour and comparative embryology; (6) the period of experimental embryology.

1. Harvey published in 1651 a treatise on embryology (“Exercitationes de Generatione Animalium”) in which are recorded observations on the development of the chick and some facts of mammalian embryology. He also discussed the nature of development and deduced from observations the important principles that all animals come from ova and that the development is a new formation, not more growth or enlargement. His study was made with simple lenses which did not enable him to trace the genesis of the embryo from its earliest stages. Malpighi, who was more of a microscopist than Harvey, outranks him as an embryologist. His work on the development of the chick, published in 1672, shows Harvey’s influence, but by means of excellent descriptions and many sketches carries the account of the development back to the close of the first day of incubation.

Only the first five periods are recognized by Locy.

2. A century later than Harvey came the work of Caspar Friedrich Wolff, whose “Theoria Generationis” was first published in 1759. At

that time embryology was dominated by the conception of pref0rma Fur. 1. William Harvey. (From Loey.)

tion which had gradually grown up around the observations of Malpighi, Leeuwenhoek, Boerhaave, and oth.'-rs. Although the point of view maintained by Wolff, that of epigenesis, had also been that of Harvey and Aristotle, he is to be regarded as the first active proponent of that doctrine. He was opposed by the great physiologist, Haller, and by Bonnet, a very prolific writer on the subject. Led by these men, the 1)1-eforination-epigenesis controversy held the attention of embryologists to the close of the eighteenth century.

3. The pmiml of von Baer really begins with the ()l).\‘C1'V2l,tl()I1S of his friend, Pander, first published in 1817. Pander established the presence

of three layers in the early embryo from which the later organs are developed. Obviously this is a conclusive argument against the old preformation views. Von Bacr, however, is responsible for the germ fiG. 2. K.ul Ernst um Bu-1 (Fmm Lot-\.l

layer doctrine as a ;1(*m‘l.lllA2l,tl()n, and fun the (‘\])()~itiOn of the manner in which the layers give rise to the later organs of the embryo. He also discovered the egg in the ovary of mammals and of man and pointed out the similarity in the mode of origin of these animals to those lower in the scale. He was the first to recognize the notochord as occurring in all vertebrate animals and to point out the value of comparative embryology for anatomy and zoology. With von Baer the modern pmiml of

(‘l!1l)I‘}’()l()gy really begins. Von Baer is often spoken of as the originator of the 1'(‘e:t1,)lt1llatl0I1 doctrine, and he did hint at it, but the formulation is due to Fritz Miillcr in 1863. Von Baer called attention to the greater similarity that exists between embryos of related groups than between adults. The younger the embryos the more alike are they. The recapitulation theory will be considered on a later page.

4. The period following von Baer is one of rich biological achievement. The discovery of the cell, nuclei, mitosis, the publication of the evolution doctrine, the birth of histology and pathology, all wrought changes in the aspects of biology that necessarily had their influence on embryology. The facts of development were harmonized by the conception of evolution, and both comparative anatomy and paleontology threw light on the reasons for some of the ()bs(‘u1'0 embryological phenomena discovered. This period saw established the relation of cells, tissues, and organs in the embryo, recognition of egg and sperm as cells, the process of fertilization, many details in the development of both vertebrates and invertebrates, and the beginnings of the doctrine of germinal continuity.

5. The period of Balfour was one of exact morphological research. Balfour was a young English embryologist (1851-1882) whose “Monograph on the Development of Elasmobranch fishes” (1878), and whose “'l‘r<-alise on (‘mnp:11'ati\<- l3lml)ryology” (1880-1881), Won the highest recognition. With improved microscopes and technique vast numbers of investigations have been undertaken since his time and the literature of the science greatly enriched. The newer science of cytology is a direct offshoot of the embryology of this period due to the pushing farther and farther back of the questions on the origin of germ cells and the fertilization and early development of the egg. One of the most notable advances of this period lay in the field of cell lineage. The investigations of the eighties and nineties established for the eggs of many animals a complete history from the one-celled egg to the larval form with definite fundaments of organs which later by specialization and elaboration make up the body of the adult. Thus is the organized character of the young embryo made clear even before the germ-layer stage. Thus also we know that in the organization of the egg there is a predetennination of the adult characters, a point of view which corresponds closely to neither of the old ideas of preformation and epigenesis.

6. While much of a morphological character remains to be learned by embryologists of the future, it is not to be supposed that the nature of the organic mechanism could be investigated only from that standpoint. With the increase of exact knowledge of the structure of the organism, we demand information as to its method of operation. To the developing animal must be applied not only the laws of physiology, with a correspondingly better understanding of the origin and development of these functions, but also the laws of physics and chemistry, and particularly physical chemistry must be appealed to. The study of development in the light of these laws is the dominant note of the embryology of the present day, and as an experimental science it is making remarkable strides forward. The present is the period of experimental embryology, although of course there are many problems of morphological character which are still to be solved.

Ancient Times

Much information and many observations known to have been accumulated, but not recorded as a body of knowledge. Systems of medicine were developed both in Greece and in Egypt in PreAristotelean times.

4-TH CENTURY, B.C. Aristotle (384—322 B.C.) made first system of classification of animals and plants, published first accounts which are extant of natural history, anatomy, and embryology. Wrote “De Generatione Animalium.”

Dissection of human body legalized in Alexandria.

2ND CENTURY, A.D. Galen compiled and brought up to date knowledge of anatomy and physiology, but without aid of human dissection.

16TH CENTURY. Vesalius (1514-1564) reformed teaching of anatomy. intro-6 HISTORICAL DEVELOPMENT OF EMBRYOLOGY

.ducing dissection and replacing appeal to ancient authorities. “Structure of Human Body” published 1543. V _ 1625. K Fabricius’ (1537-1619) treatise on development of chick published. ‘1,7'1jH'C1:N'rURY. Harvey (1578-1667) instituted experimental study of living animals. Announced discovery of circulation of blood in 1616; published .“De ’Motu Cordis et Sanguinis” in 1628. Published in 1651 “De Generations Animalium,” an embryological treatise. Invention of compound microscope had occurred by early years of seven! teenth century and it was applied to biological uses by middle of '- century. 16-15. Severinus (1580-1656) published “Zootomia Democritae” giving anatomical descriptions of comparative type of some vertebrates, and some developmental stages.

1665. Hooke (1635-1703) published “Microgr:iphia.”

16,66. Redi experimentally disproved spontaneous generation of life among insects.

1669., Malpighi (1628-1694) published “Anatomy of Silkworm.”

1672. Malpighi published two works on embryology: “De Formatione Pulli in Qvo,” and “De Uvo Incubate.”

Swaiiiinerdam (1637-1680) studied development of butterfly and by analogy to pupa thought earlier organs were preformed in egg (not published until 1737).

1675. Leeuwenhoek discovered spermatozoa (also attributed to Hamm,

' a medical student). Leeuwenhoek accordingly became a strong preforlniationist, adhering to the school of the “spermists.” 18TH CENTURY. 1713. Leeuwenhoek discovered parthenogenesis in plants. ' 1735. ‘Linnaeus (1707-1778) published first edition of “Systcma Naturae.” ' In 1753 he introduced the binomial system of nomenclature in “Species

‘ Plantarum,” and in 10th edition of “Systema Naturae” in 1758.

1759. Wolff (1733-1794) published “Theoria Gcnerationis” in defence of position of epigenesis.

1768. He published “De Formatione Intcstinorum,” the greatest master‘piece of embryology before V011 Bacr.

1799. Cuvier (1769-1832) founded comparative anatomy.

19TH CENTURY. 1800. Bichat (1771—1801) founded histology. ’ ' 1812. Cuvier founded vertebrate paleontology.

1817. Pander (1794-1865) recognized three primary body layers in chick.

18:24. ' Prevost and Dumas saw segmentation in animal egg.

1828. "Von Baer (1792-1876) published “Entwicklungsgesehichte der "1‘iere.” Founded embryology as a science. Established the doctrine of germ layers. Made embryology comparative. Proposed a theory of recapitulation.

1831., Robert Brown (1773-1858) discovered the nucleus.

1835. Dujardin (1801-1862) discovered living matter, sareode, in lower animals. EVENTS OF IMPORTANCE IN THE HISTORY OF EMBRYOLOGY 7

1838. Schwann (1810-1882) with Schleiden (1804-1881) founded cell theory.

1841. Remak (1815-1865) figured cell division (amitosis). His work and that of Kiilliker laid foundations for a theory of cell division.

1846. Von Mohl (1805-1872) observed protoplasm in plants and named it.

1851. Newport observed entrance of sperm of frog into egg.

1856. Von Siebold (1804-1885) described parthenogcnesis.

1858. Virchow (1821-1903) published “Cellular Pathology.” Omnis cellula e cellula.

1859. Darwin (1809-1882) published “Origin of Species.”

1861. Kolliker (1817-1905) published general treatise on embryology. Studied segmentation of egg.

1861. Max Schultze (1825-1874) formulated protoplasin doctrine.

1863. Muller (1821-1897) propoundcd rccapitulation doctrine.

1865. Sperms recognized as cells.

1866. Mendel (1822-1884) published studies on inheritance.

1866. Kowalcvsky (1840-1901) showed that all animals pass through gastrula stage.

1862-1869. Pasteur (1822-1805) and Tyndall (1820-1893) disproved spontaneous generation.

1868. Use of stains in study of cells and protoplasm introduced.

1870. His (1831-1904) introduced use of microtome.

1873. Anton Dohrn (1840-1909) founded the Naples Zoological Station.

1874. Haeckel (1834-1919) proposed gastrea theory.

1874. Balfour and Foster published “Elements of limbryology.”

1875. fleininiiig (1843-1905) discovered centrosome.

1875. Strasburger (1844-1912) first figured adequatel_v chromosomes and cell division.

1878. Whitman (1842-1910) published “l7.mbryology of Clepsine,” which with Ma1'k’s (1847— ) paper on “Maturation, Fecundation, and Segmentation of Limax” began the studies which became known as cell lineage in the next two decades.

1879. flemming distinguished between direct and indirect types of cell division. ‘

1880—1881. Balfour (1851-1882) published “Comparative Embryology.”

1882. flemming discovered longitudinal split of chromosomes.

1883. Roux (1850-1924) began studies of experimental embryology using frog’s egg.

1891. Weismann (1834-1914) published theory of germ plasm.

Since 1890 the advances of embryology have been so numerous and so many investigators have been concerned that it is impossible now to choose between them as to historical significance.

Bibliographic Note

Among the more important accounts of the subjects contained in this chapter are the following: Locy, Osborne, Foster, Wilson, Gerould, Hertwig, and Nordenskiold. These works are cited in full in the bibliography on page 406.

1931 Richards: Part One General Embryology 1 Historical Development of Embryology | 2 The Germ-Cell Cycle | 3 Egg and Cleavage Types | 4 Holoblastic Types of Cleavage | 5 Meroblastic Types of Cleavage | 6 Types of Blastulae | 7 Endoderm Formation | 8 Mesoderm Formation | 9 Types of Invertebrate Larvae | 10 Formation of the Mammalian Embryo | 11 Egg and Embryonic Membranes | Part Two Embryological Problems 1 The Origin And Development Of Germ Cells | 2 Germ-Layer Theory | 3 The Recapitulation Theory | 4 Asexual Reproduction | 5 Parthenogenesis | 6 Paedogenesis And Neoteny | 7 Polyembryony | 8 The Determination Problem | 9 Ecological Control Of Invertebrate Larval Types

Cite this page: Hill, M.A. (2021, April 23) Embryology Book - Outline of Comparative Embryology 1-1. Retrieved from

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