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.

    52/342 (page 36)
    The third maxillipede may be regarded as the mean type of the average thoracic appendages. Compared with it the other appendages exhibit a true alternative development of their parts. When the exopodite is large the endopoditc is small, and vice versd. Besides these general modifications in which the degenerative evolution of the entire appendages is exhibited, each one of the segments undergoes certain modifications of its own. Fig. 8.—Astacus fluviatilis. Third left maxillipede (1,5/1): co, coxopodite,and ba, basipodite, forming pr, protopodite; br, gill; ex, exopodite ; en, en- dopodite (Huxley). Fig. 9.—Astacus fluviatilis. Second left maxillipede (1,5/1): co, coxo- podite, and 6a, basipodite, forming pr, protopodite ; en, endopodite, ex, exopodite ; br, gill (Huxley). In the second maxillipede (fig. 9), which much resembles the third, the exopodite (ex.) is large, and the endopodite (en.) is small, the prodopod,ite (pr.) is better developed, and the podobranch (br.) has begun to atrophy. The same evolution is exhibited by the first