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Updated: May 14, 2025
The studies of such individuals as John Standard reporting the weight of various parts of the hen's egg, e.g., the shell, the yolk, the white, reveal the wing of embryological investigation that was increasingly obsessed with quantification and the physicochemical analysis of the embryo and its vital functions.
In order to appreciate this important feature, we have distributed the embryological phenomena in two groups, palingenetic and cenogenetic. Under palingenesis we count those facts of embryology that we can directly regard as a faithful synopsis of the corresponding stem-history.
Even gross anatomy has much to gain from the careful, systematic examination of these organisms. With still greater force this statement applies to the studies of finer structural relations. Little is known concerning the embryological development and life history of certain of the primates, and almost nothing concerning their pathological anatomy.
We see why certain characters are far more serviceable than others for classification; why adaptive characters, though of paramount importance to the beings, are of hardly any importance in classification; why characters derived from rudimentary parts, though of no service to the beings, are often of high classificatory value; and why embryological characters are often the most valuable of all.
He had already been the teacher of Karl Ernst von Baer; and though the pupil outran the master, and has become the pride of the scientific world, it is but just to remember that he owed to him his first initiation into the processes of embryological research.
For, as I have recently remarked in regard to the members of each great kingdom, such as the Vertebrata, Articulata, etc., we have distinct evidence in their embryological, homologous, and rudimentary structures, that within each kingdom all the members are descended from a single progenitor. When the views advanced by me in this volume, and by Mr.
And this is true from the first or embryological inception of the dog-unit or "germ," until the real occupant of the dog-tenement dismisses his bioplastic weavers, and lies down to die. And so of all vital units. Each determines its own structural form, and unchangeably retains it to the end, even to the slightest impression of a scar inflicted years and years before.
Hence we can see how it is that resemblances in several unimportant structures, in useless and rudimentary organs, or not now functionally active, or in an embryological condition, are by far the most serviceable for classification; for they can hardly be due to adaptations within a late period; and thus they reveal the old lines of descent or of true affinity.
In drawing up the several series he trusts chiefly to embryological characters, but receives aid from homologous and rudimentary organs, as well as from the successive periods at which the various forms of life are believed to have first appeared in our geological formations. He has thus boldly made a great beginning, and shows us how classification will in the future be treated.
In most modern fishes and in all higher vertebrates the notochord is gradually removed as the bodies of the vertebrae are formed about it; but in the Devonian fishes it persists through maturity and the vertebrae remain incomplete. THE SKELETON IS CARTILAGINOUS. This also is an embryological characteristic.
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