ORIGIN OF THE WHALES. 26 1 



Hoofed animals among the Indeciduata. In the same way 

 as the river-horse at present stands midway between the 

 extreme branches of oxen and sea oxen, the sea otter still 

 forms a surviving intermediate stage between the widely 

 separated branches of dogs and sea dogs. In both cases 

 the complete transformation of the external form, conse- 

 quent upon adaptation to entirely different conditions of 

 life, has not been able to efface the solid foundation of the 

 inherited internal peculiarities. 



According to Huxley's opinion, which has already been 

 quoted, only the Herbivorous Whales (Sirenia) are derived 

 from Hoofed animals ; on the other hand, the Carnivorous 

 Cetacea (Sareoceta) are derived from the marine animals of 

 prey; the Zeuglodonts would form a transition between the 

 two latter. But in this case it would be difficult to under- 

 stand the close anatomical relations which exist between 

 the Herbivorous and Carnivorous Cetacea. The strange 

 peculiarities in the internal and external structure which 

 so strikingly distinguish the two groups from all other 

 mammals would then have to be regarded only as analogies 

 (caused by the same kinds of adaptation), not as homologies 

 (transmitted from a common primary form). The latter, 

 however, strikes me as being by far the more probable, and 

 hence I have left all the Cetacea among the Indeciduata as 

 OTie group of kindred origin. 



The remarkable order of Flying Mammals, or Bats 

 (Chiroptera), stands near to the Camaria as well as to the 

 Insectivora. It has become strikingly transformed by adap- 

 tation to a flying mode of life, just as marine animals of 

 prey have become modified by adaptation to a swimming 

 mode of life. This order probably also originated out of 



