2.54 THE MAMMALIA. 



have no idea in what period or under what circum- 

 stances whales came to be developed. "What is 

 improbable is that they were descended directly 

 from reptile-like ancestors, independently of the 

 other mammals. None of their peculiarities point 

 directly to the Keptiles, and are all intelligible as 

 modifications which were effected by the land 

 animal in its transition to a life in water. 



But of what kind were these ancestors ? Our 

 first thought turns to the Seals, which, of course, 

 have likewise adapted themselves to an aquatic 

 life. However, in their case, the hind limbs have 

 not in any way become reduced, and have only 

 changed their position to the pelvis ; whereas the 

 upper and lower parts of the leg are shortened, and 

 the feet have become broad and lengthened paddles. 

 Hence it cannot be imagined that these animals, 

 which are so admirably equipped for swimming, 

 could have struck out a new kind of adaptation. 

 There could not have been any use or necessity 

 for this. Hence a certain resemblance in the 

 teeth can only have been the result of convergence ; 

 and Prof. Flowers reminds us that this had long 

 since been pointed out by Hunter, 1 who says : 



1 John Hunter, ' Observations on the Structure and Economy 

 of Whales,' Philoso. Trans. 1787. 



