Evolution by atrophy in biology and sociology / by Jean Demoor, Jean Massart, Émile Vandervelde ; translated by Mrs. Chalmers Mitchell.

  • Demoor, J. (Jean), 1867-1941.
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: Evolution by atrophy in biology and sociology / by Jean Demoor, Jean Massart, Émile Vandervelde ; translated by Mrs. Chalmers Mitchell. Source: Wellcome Collection.

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    the original formation of these organs in their ancestral forms, their development in the indivi- dual, the phylogenetic evolution of function, and the great variation resulting from individual adaptation. Before entering upon our immediate subject, it would be as well to define its limits by saying a few words concerning the questions not under immediate consideration. 1. Original formation of organs in ancestral forms.—Little is known concerning the primary origin of organs, and their development before their assumption of the aspect and function by which we know them. What were the rudimentary leaves like in the ancestors of flowering plants ? What were the eyes of the first vertebrates like ? Did these organs develop from existing organs ful- filling other functions, or were they formed inde- pendently ? However that may be, if they arose from other organs, we know nothing of the modifi- cations which they underwent; and if they were formed independently, we need not discuss the fact here, for in that case the organ would not have developed by transformation. Having once been formed, it would develop and improve, and this process would not necessarily have been attended by partial degeneration. 2. Development of organs in the individual.— In the course of embryological development, organs do not exactly repeat the successive phases