72 



THE GENESIS OF SPECIES 



[Chap. 



ill tlie independent development of two closely similar 

 forms. Ill all cases, no doubt (uii this same theory), f^ome 

 adaptation to habit or need would gradually be evolved, but 

 that adaptation would surely be arrived at by dillerent 

 loads. 



The organic world supplies us with multitudes of ex- 

 amples of similar functional results being attained by the 

 most diverse means. Thus the body is sustained in the air 

 by birds and by bats. In the first case it is so sustained 

 by a limb in wliich the bones of the hand are excessively 

 reduced, Ijut ^\•hich is provided with immense outgrowths 



W1NU-UUNE8 OF PTERODACTYLE, BAT, ANIJ RIRI' 



from the skin — namely, the feathers of the wing. In tlie 

 second case, however, the body is sustained in the air by a 

 limb in which the bones of the hand are enormously 

 ncrcased in leiigtli, and so sustain a great expanse of naked 

 kin, which is the Hying membrane of the bat's wing. 

 Certain fishes and certain reptiles can also flit and take 

 very prolonged jumps in the air. The llying-fish, however 

 takes these by means of a great elongation of the rays of 



