The Evolution of Man — Volume 1

The remarkable processes of gastrulation, ovum-segmentation, and formation of germinal layers present a most conspicuous variety. There is to-day only the lowest of the vertebra...

In order to understand clearly the course of human embryology, we must select the more important of its wonderful and manifold processes for fuller explanation, and then proceed...

Among the many interesting phenomena that we have encountered in the course of human embryology, there is an especial importance in the fact that the development of the human bo...

The earliest stages of the human embryo are, for the reasons already given, either quite unknown or only imperfectly known to us. But as the subsequent embryonic forms in man be...

The vertebrate stem, to which our race belongs as one of the latest and most advanced outcomes of the natural development of life, is rightly placed at the head of the animal ki...

The two "primary germinal layers" which the gastraea theory has shown to be the first foundation in the construction of the body are found in this simplest form throughout life...

There is a substantial agreement throughout the animal world in the first changes which follow the impregnation of the ovum and the formation of the stem-cell; they begin in all...

The field of natural phenomena into which I would introduce my readers in the following chapters has a quite peculiar place in the broad realm of scientific inquiry. There is no...

We owe so much of the progress of scientific knowledge to Darwin's Origin of Species that its influence is almost without parallel in the history of science. The literature of D...

We have now secured a number of firm standing-places in the labyrinthian course of our individual development by our study of the important embryonic forms which we have called...

We may distinguish three chief periods in the growth of our science of human embryology. The first has been considered in the preceding chapter; it embraces the whole of the pre...

The recognition of the fact that every man begins his individual existence as a simple cell is the solid foundation of all research into the genesis of man. From this fact we ar...

BLAST-: (in compounds) pertaining to the early embryo (blastos = a bud); hence:-- Blastoderm: skin (derma) or enclosing layer of the embryo. Blastosphere: the embryo in the holl...

It is in many ways useful, on entering upon the study of any science, to cast a glance at its historical development. The saying that "everything is best understood in its growt...

two sections of the science of evolution--between the evolution of the individual and that of his ancestors. We have formulated this connection in the biogenetic law; the shorte...

in the oviduct. Either here in the oviduct or after the mammal gastrula has passed into the uterus it is converted into the globular vesicle which is shown externally in Figure...

The three higher classes of vertebrates which we call the amniotes--the mammals, birds, and reptiles--are notably distinguished by a number of peculiarities of their development...

primitive vertebrate they probably had the same form as in the actual amphioxus--the primitive kidneys (protonephra). These are originally made up of a double row of little cana...

We must count it an important advance that we are thus in a position to reduce all the various embryonic phenomena in the different groups of animals to these four principal for...

Moreover, one could feel nothing of the testicles in the inguinal canal. On the other hand, the male organ was very small, but normally developed. It was clear that this apparen...

The embryology of man and the animals, the history of which we have reviewed in the last two chapters, was mainly a descriptive science forty years ago. The earlier investigatio...