106 A BOOK OF' WHALES 



i.e., the likeness is superficial and due to similar 

 conditions, not similar descent. This convergence 

 is not an uncommon fact in nature. Such likenesses 

 as there are between the seals and the whales and 

 between the Manatees and the whales are examples. 

 "Flying' Rodents and "Flying' Marsupials exhibit 

 another instance of the same phenomenon. 



In technical zoological parlance then, by those who 

 believe the whales to be two groups originally distinct 

 from each other which have come to lie side by side, 

 they would be spoken of as " diphyletic." That there 

 do not appear to be any annectant forms between the 

 toothed and the whalebone whales is so far in favour 

 of this view. But much more than that is necessary 

 to lend even a colour of probability to the suggestion. 



It is perfectly true that the two great divisions of 

 the M^stacoceti and the Odontoceti are, as wUl be 

 seen from the definitions which follow, separated from 

 each other by exceedingly trenchant characters ; so, 

 for the matter of that, are the Archaeoceti from both. 

 But what appears fatal to us to the idea of a double 

 origin is the exact correspondence in certain structures, 

 which, so to speak, need not necessarily have been 

 the same. Among these the peculiar form of the 

 scapula stands pre-eminent. It is only in whales, 

 and it is in all whales, that this shape of scapula 

 is met with. 



