File:Evolution by atrophy in biology and sociology (1899) (14577458579).jpg

Identifier: evolutionbyatrop00demo (find matches)
Title: Evolution by atrophy in biology and sociology
Year: 1899 (1890s)
Authors: Demoor, J. (Jean), 1867-1941 Massart, Jean, 1865-1925 Vandervelde, Emile, 1866-1938 Mitchell, Chalmers, Mrs
Subjects: Sociology Evolution
Publisher: New York : D. Appleton and Company
Contributing Library: University of British Columbia Library
Digitizing Sponsor: University of British Columbia Library

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todus)have best preserved the bipinnated fin. InCeratodus especially it is exhibited in almost theprimitive condition. Gradually, however (as inOrthacantlius), the rods situated along one edgeof the principal rod disappeared, and the fin, nolonger bipinnated, became unilateral. This pro-gressive transformation entailed the disappearanceof nearly half of the fin. With creatures which have become adapted to aterrestrial life, the limbs—so far as can be judgedfrom what is known at present—appear to haveundergone the following transformations: The bi-pinnated fin (such as that of Ceratodus) (fig. 18)is always the starting-point. Then the lateral rodsof one half almost completely disappear (as in(Protopterus Amphibius). Next, the other halffollows (as in P. annectcus) (fig. 19), and finallyonly the principal rod remains (as in Lcpidosiren)(fig. 20). At this point the limbs are reduced to merelopped stems; they have not, however, atrophied;the degeneration which has accompanied this de-
Text Appearing After Image:
Fig. 20.—Lepidosiren paradoxa, F

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