2 S THE SCIENTIFIC EVIDENCES OF 



rudiments, and directed backwards, so as to be 

 of no use for walking, but serving to com- 

 plete the fish-like taper of the body. But 

 in the whales the modification has gone even 

 further than this, so that the hind legs 

 have ceased to be apparent externally, and are 

 only represented internally by remnants so 

 rudimentary that it is impossible to make out 

 with certainty the homologies of the bones; 

 moreover, the head and the whole ] body have 

 become completely fish-like in shape. But pro- 

 found as these changes are, they only affect 

 those parts of the organism which it was for 

 the benefit of the organism to have altered, so 

 that it might be adapted to an aquatic mode 

 of existence. Thus the arm, which is used as 

 a fin, still retains the bones of the shoulder, 

 fore-arm, wrist, and fingers, although they are 

 all inclosed in a fin-shaped sack, so as to 

 render them quite useless for any other purpose 



