26 FOOT-NOTES TO EVOLUTION. 



surroundings in which they come into perfect adjust- 

 ment. A partial adjustment must with time become a 

 complete one, for the individuals not adapted will be 

 exterminated in the struggle for life. 



Everywhere in Nature there is the closest adap- 

 tation of life to its conditions. But this adaptation 



must come about through the survival 

 How selection ^r 4.u • c^^ . . ,■ , 



^ d those organisms fittest to live under 



tation. these conditions, while the unfit die out 



and leave no progeny. Thus, in the 

 words of Professor Bergen, " with much the same result 

 as that which the farmer obtains by selecting his seed 

 corn, the gardener by thinning out his beds, or the 

 cattle-raiser by selling off his roughest calves for veal, 

 Nature is at work on an inconceivably great scale, thin- 

 ning out the least perfect individuals of each species," 



But the thinning-out process is not the whole of 

 "natural selection." Other influences work in connec- 



tion with this. In the higher animals 

 Acceleration of , , , , 



development. changes may be wrought by conscious 



or unconscious effort on the part of the 

 creatures themselves, and the power to put forth such 

 effort may be perpetuated by " natural selection." Cer- 

 tain organisms may carry their growth farther than their 

 ancestors have done, so that the completed structures 

 of their ancestors would be with them only a stage of 

 development. And, as Professor Cope has shown, devel- 

 opment may be hastened by the abridgment or omis- 

 sion of useless stages. Thus the ultimate maturity of 

 the animal may be carried to a degree of specialization 

 beyond that of its ancestry. If this "accelerated de- 

 velopment " be for the gain of the species, " natural 

 selection " will cause it to be retained. We may prop- 

 erly include under " natural selection " all those changes 

 which come from the special use or disuse of any part 



