. Evolution and its relation to religious thought . ages corresponding to jaw-feet become walk-ers ; and even what corresponds to antennae or sense-appendages, may, as in branchippus, become powerfulclaspers. Finally, in all the lowest crustaceans, theidentity is evident, because all the segments and theirappendages are much alike in form and function (). We have taken exaaiples from near the middle of thearticulate scale, because, as already stated, both the essen-tial identity and the adaptive modifications are easily 122 EVIDENCES OF THE TRUTH OF EVOLUTION. traced. If we go downward i
. Evolution and its relation to religious thought . ages corresponding to jaw-feet become walk-ers ; and even what corresponds to antennae or sense-appendages, may, as in branchippus, become powerfulclaspers. Finally, in all the lowest crustaceans, theidentity is evident, because all the segments and theirappendages are much alike in form and function (). We have taken exaaiples from near the middle of thearticulate scale, because, as already stated, both the essen-tial identity and the adaptive modifications are easily 122 EVIDENCES OF THE TRUTH OF EVOLUTION. traced. If we go downward in the scale, the structurebecomes more and more generalized, and the rings andappendages become more and more alike (Fig. 31), untilin the most generalized forms we have only a series ofsimilar rings, with similar pairs of appendages, exceptsome necessary modifications to form the head and is well shown in the centiped (Fig. 32), and stillbetter in marine worms (Fig. 33). In some marineworms the slight modification to form the head takes. Fig. 33.—Syllis prolifera. place under our very eyes. These often multiply by di-viding themselves into two. When they do so, they makea new head and new tail by slight modification of seg-ments and appendages (Fig. 33). If, on the other hand, we go up the scale, we findadaptive modifications obscuring more and more thesimple and obvious identity of parts, until finally theidentity can not be recognized without extensive com-parison in the taxonomic series and study of embryonicconditions. In crabs—which is a higher form than cray-fisli—the tail or abdomen seems to be wanting, but is onlyvery sijpiall and bent under the body and thus all essential respects the structure is precisely like the HOMOLOGIES OF THE ARTICULATE SKELETON. 123 cray-fish. In fact, in the embryo, we trace the one forminto the other ; for the crab is at first a long-tailed crus-tacean (Fig. 34). Insects are the highest form of articulates. In t
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