IN MODERN SCIENCE. 



85 



well as in many higher vertebrates, we find less 

 than five digits. But in all these cases it can 

 be shown that separate digits have retrograded, 

 and have finally been completely lost. The 

 causes which affected the development of the 

 five-fingered foot of the higher vertebrates in 

 this amphibian form from the many-fingered 

 foot (or properly fin), must certainly be found 

 in the adaptation to the totally altered functions 

 which the limbs had to discharge during the 

 transition from an exclusively aquatic life to one 

 which was partially terrestrial. While the many- 

 fingered fins of the fish had previously served 

 almost exclusively to propel the body through 

 the water, they had now also to afford support 

 to the animal when creeping on the land. This 

 effected a modification both of the skeleton and 

 of the muscles of the limbs. The number of fin- 

 rays was gradually lessened, and was finally re- 

 duced to five. These five remaining rays were, 

 however, developed more vigorously. The soft 

 cartilaginous rays became hard bones. The rest 

 of the skeleton also became considerably more 

 firm. The movements of the body became not 

 only more vigorous, but also more varied ;" and 

 the paragraph proceeds to state other ameliora- 

 tions of muscular and nervous system supposed 



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