Darwin's own views of the bearing of the facts of embryology upon questions of wide scientific interest are perfectly clear.
My desire has been to write a chapter showing the influence of Darwin's work so far as Embryology is concerned, and the various points which come up for consideration in discussing his views.
Thus the valuable aid of embryologyis obtained in determining relationships.
But a deeper reason than this has been assigned for the importance of embryology in classification.
Some preliminary knowledge of embryology is essential to understand the formation of branchial fissures, and we refer the reader to any of the standard works on embryology for this information.
Hand in hand with embryology it has been the subject of much investigation in this century, and to enumerate the workers of the present day who have helped to bring about scientific progress would be a task of many pages.
Another important fact shewn by embryology is that the central nervous system, and percipient portions of the organs of special sense, especially of optic organs, are often formed from the same part of the primitive epidermis.
The very heterogeneous character of the Ganoid group is clearly shewn both in its embryology and its anatomy.
Amongst the Sauropsida the Aves have for obvious reasons received a far fuller share of attention than any other group; and an account of their embryology forms a suitable introduction to this part of our subject.
It is only within quite recent times that any investigations have been made on the embryology of this heterogeneous, but primitive group of fishes.
It is obvious that in dealing with the light thrown by embryology on the ancestral form of the Chordata the significance of this peculiar character of the head of many vertebrate embryos must be discussed.
Embryology does not however add anything to the anatomical evidence on this subject.
General observations on theembryology of Ganoids, p.
Huxley took the embryology of the dog as an example of the process in the higher animals generally, and as it had been worked out in detail by a set of investigators.
These facts are those which are classed by biologists under the heads ofEmbryology and of Palaeontology.
Comparative embryology shows that, however varied the forms and functions of the numerous animal organs may be, the method of their development is remarkably similar.
For the decision of a question so momentous as the relative scopes of evolution and epigenesis in embryology must have an important bearing on the future of biology, upon its aim and the method of research.
Then the scientific world perceived the truth and accepted the evidence, inaugurating those studies in embryology which shed so much luster on the nineteenth century.
A dense fog obscured all minds, and the dazzling truth could not pierce it; thus all progress in embryology was precluded.
The embryology of turtles throws light upon the fossil chelonians.
Embryology has shown that the portion of the head in front of the mouth is also composed of three segments.
Its anterior portion appears from embryology to be very primitive.
That the mouth of an animal can migrate seems at first impossible, but if we had time to examine the embryology of annelids and insects, it would no longer appear inconceivable or improbable.
If we appeal from adult anatomy to embryology the case becomes all the worse for us.
And this study of embryology brought to light many new and interesting facts.
But many facts of embryology and comparative anatomy point to such a form as a very possible ancestor of all forms higher than flat worms, viz.
In embryology the true stereoscopic image shows the relative position of important details.
Under the influence of this work, Elie, who until now had limited himself to introductory researches, resolved to concentrate all his efforts on the comparative embryology of animals.
It can only be filled by hypotheses, based upon the embryologyof those animals which, in their embryonic development, repeat the inferior forms from which they are derived, thus reflecting the general evolution of living beings.
Tired with all these things, he left Naples for Trieste, where he carried out successful researches into the transformations of Echinodermata, from the point of view of Comparative Embryology and genetic connections between inferior animals.
He studied the embryology of the green-fly from the genealogical point of view, and went to Munich for the summer term in order to work with the celebrated zoologist von Siebold, a typical and venerable old German scientist.
He resigned himself to the study of the embryology of sea-urchins in order to fill a few lacunae in his previous researches.
In spite of very difficult conditions and of the persistent weakness of his eyesight, he succeeded in filling the lacuna in the embryology of the Geophilus.
The scantiness of the marine fauna was a bitter disappointment; he had to fall back upon what little he found, and embarked on the study, hitherto unknown, of the embryology of Myriapoda.
At last, in the spring, we started for Villefranche, where he immediately set to work with success upon the embryology of jelly-fish; an important monograph on that subject was published by him in 1886.
Later, in 1867, they shared the Baer Prize of the Petersburg Academy for their discoveries in embryology (p.
The latter was too old already to be troubled with pupils, and Elie studied his insect embryology independently; however, he visited the old man assiduously, and they had long scientific conversations.
Von Baer and Agassiz added to this comparison in the ontogenic series also, and comparison of these two series with each other, and therefore the application of embryology to the classification of animals.
That the embryonic development of one of the higher representatives of any group repeated in a general way the terms of the Taxonomic series in the same group, and therefore that embryologyfurnished the key to a true classification; and, 2.
An important fact in its favour was discovered by Laurie (17), who investigated the embryology of two species of Scorpio under Lankester's direction.
Morgan, "Embryology and Phylogeny of the Pycnogonids," Biol.
For information as to the embryology of scorpions, the reader is referred to the works named in the bibliography below.
While recognizing the importance of comparative embryology in the study of descent, Gegenbaur laid stress on the higher value of comparative anatomy as the basis of the study of homologies, i.
I rather doubt whether you see how far, as it seems to me, the argument for homology and embryology may be carried.
This seems to me the most interesting discovery in embryology which has been made for years.
The evidence of embryology is decidedly against the view that the eye-stalks are limbs.
They are of interest, however, rather from the point of view of general embryology than from that of the special student of the Crustacea, and cannot be fully dealt with here.
The embryology of Callianira has been worked out by E.
In some speculations concerning the embryology of Loranthus he came, by a wrong line of approach, within touch of the right comparison, when he compares the endosperm to the confervoid green growth (i.
I mean questions ofEmbryology and questions of Race.
But taking this anticipation for granted, as it is fully realised by the facts of embryology, it follows that the science of embryology affords perhaps the strongest of all the strong arguments in favour of evolution.
Proofs of our Animal Origin The Extraordinary Affinity of Bodily Structure The Revelations of Embryology The Tale Told by the Useless Rudimentary Organs Sec.
This is in two volumes, copiously illustrated, of which the first is entirely devoted to human embryology or ontogeny, a branch of science which furnishes the most overwhelming evidence.
Darwin, Vogt, and Haeckel, in their attempts to support the theory of the animal origin of man, had not sufficient knowledge of the embryology of monkeys.
Is there any fallacy in speaking of the Embryology of the New Life?
The classification, therefore, is based, from the scientific side on certain facts of embryology and on the Law of Biogenesis; and from the theological side on certain facts of experience and on the doctrine of Regeneration.
It has long been felt that embryologyand rudimentary structures indicated community of descent.
But if we are to admit the human point of view, a glance at the facts of embryology must produce very uncomfortable reflections.
Notes on theEmbryology and Classification of the Animal Kingdom," Q.
Embryology enters therefore into the closest connection with comparative anatomy.
Between comparative anatomy and embryologythere exists a close connection, for the one throws light on the other.
Thus Vogt, who was later to become one of the protagonists of materialism in Germany, developed in his memoir on the embryology of Coregonus[293] the theory of the independent or individual life of the cell.
What interests us chiefly in the work of this embryological period is, of course, the relation of embryology to comparative anatomy and to pure morphology.
This second volume is intended as an introduction to embryology for the use of doctors and science students.
This recognition of the parallelism between comparative anatomy and embryology is, of course, the kernel of the Meckel-Serres law.
He could prove from embryology that the jaws were not the equivalent of limbs, as so many Okenians believed.
These praiseworthy investigations supply from the realm of embryology new and welcome foundations for comparative anatomy" (p.
The hypothetical ancestor of the insects, as restored by Tothill from the evidence of embryology and comparative anatomy, is an animal more easily derived from the Chilopoda than from the Trilobita.
The adult selachian venous system is therefore to be considered as illustrating the following conditions above encountered in our study of the embryology of the mammalian venous system.
In the following pages an attempt has been made to emphasize the value of Embryology and Comparative Anatomy in elucidating the difficult and often complicated morphological problems encountered in the study of human adult anatomy.
The purpose is not to present the embryology of this portion of the vertebrate body, but to utilize certain embryological facts in order to explain the complicated adult conditions encountered.
The first and most important result of the science of Embryology was one for which the scientific world was wholly unprepared.
Within the vertebrate stem there is, as we have already seen, so complete an agreement in structure and embryologythat it is impossible to doubt their phylogenetic unity.
Virginia, on the embryology of which Selenka has given us a valuable work (cf.
It meets with difficulties equally great and insuperable in embryology and in phylogeny.
The chief result that we obtain from its embryology is the complete agreement with that of the Amphioxus in the earliest and most important embryonic stages.
In order to understand the embryology of the human vertebral column we must first carefully consider the shape and connection of the vertebrae.
When we approach this task, we find an auxiliary of the utmost importance in the comparative anatomy and embryology of two lower animal-forms.
Thus the embryology of the Amphioxus and the Ascidia has so much increased our knowledge of man's stem-history that, although our empirical information is still very incomplete, there is now no defect of any great consequence in it.
While these important results of comparative embryology have been throwing further light on the close blood-relationship of man and the anthropoid apes in the last few years (Chapter 1.
We may now turn to the embryology of the Ascidia, an animal that seems to stand so much lower and to be so much more simply organised, remaining for the greater part of its life attached to the bottom of the sea like a shapeless lump.
