62 THE PROBLEMS OF EVOLUTION 



not just the same as a character which fits the 

 individual to cope with the inciting stimulus. We 

 must admit the truth of Cunningham's statement 

 that adaptive and non-adaptive characters are 

 distinctly different, if only in this matter of origin, 

 whether or not we agree with his conclusion that 

 "their origin and evolution are entirely distinct 

 and different." ^ It is exceedingly risky to general- 

 ize concerning origin on the basis of adaptive value. 



It is significant that the individual receives a 

 normal complement of adaptive structures as a 

 part of its heritage, while its response to a fluctuat- 

 ing environment involves the adjustment of these 

 structures through its power of individual adapta- 

 bility. It may be called upon during its life to meet 

 many fluctuations of environment; it does so, not 

 by producing new organs, but by the modification 

 of the things already present in its body. The tan- 

 ning of our skin is not a deposition of pigment 

 where none existed, but only an increase of the 

 normal deposit. 



Adaptation in the individual may be looked 

 upon, therefore, as a process or a variety of proc- 

 esses giving rise to modifications of hereditary 

 equipment in response to the fluctuations of envi- 

 ronment. The nature of the process is obscure. It 

 has been admirably discussed by Conklin,^^ and for 



" Hormones and Heredity, p. 21, 1921. 



10 Rioe Institute Pamphlet, Vol. VIII, pp. 299-380, 1921. 



