58 UNIVERSALITY OF DEGENERATIVE EVOLUTION 



clumsy five-toed animal which lived in swamps. As 

 the horse type was evolved, the legs, which originally 

 only served to support the weight of the body in a 

 slow progress, were gradually adapted to running. 

 This modification was certainly advantageous to the 

 animal, as it enabled it to escape more easily from 

 its enemies. It was, however, accompanied by de- 

 generation, for the ancestor of the horse lost first the 

 great toe, then the fifth, and next the second and 

 third toes became so reduced that eventually only 

 one toe remained functional. 



Adaptation to running was effected differently 

 with the ruminants, but it was equally accompanied 

 by degeneration. With them, first the great toe 

 disappeared, then the second and fifth became simul- 

 taneously much smaller, while the third and fourth 

 continued to increase equally in length. In process 

 of time the second and third toes entirely disap- 

 peared, and the metatarsals of the third and fourth 

 joined together to form the cannon bone. In this 

 way mammals were evolved with cloven hoofs and 

 adapted to running. 



4. Adaptation to flying. There are three types 

 of animals among the vertebrates : birds, ptero- 

 saurians, and flying bats, by which is meant, not 

 those bats which are merely able to float in the 

 air like a parachute, but those which can both raise 

 and guide themselves during flight. 



(a) Birds. We have seen that the ancestor of 

 all terrestrial vertebrates was a five-toed animal. 



