COMPARATIVE ANATOMY OF MAMMALIA. 



319 



arm and hand, shows us, however, that they are both intrinsically 

 alike as in the anterior fin of the whale we distinctly perceive 

 the bones which belong to our own anterior extremities. But 

 the arm, which in all its parts is freely moveable in man, is here 

 closely attached to the body; and the hand which, obedient 

 to our rational will, performs so many wonderful works is in 

 the whale covered with a thick skin, which prevents all in- 

 dividual action of the fingers, and converts the member into a 

 simple oar, such as best suits the animal's peculiar mode 

 of life. 



The same absence of hind-legs characterises the manatees and 

 dugongs, but here the paddles or forefins are more free in their 

 movements, and exhibit rudiments of nails, by the aid of which 



Skeleton of Seal. 



these unwieldy creatures drag themselves along the shores of 

 gulfs and estuaries, to browse on the marine 

 algae which constitute their food. 



In the walrus and the large family of seals, 

 which have been formed to inhabit both the sea 

 and the land, the forelimbs are still more deve- 

 loped ; and short hinder extremities, with distinct 

 toes, joined by a swimming membrane, and well 

 adapted both for rapidly cleaving the waters 

 and slowly progressing on solid ground, assume 

 the part of the receding tail. 



Among the other mammalia which seek their prey in the 



Hinder Extremities 

 of Seal. 



