288 THE PRINCIPLES OF HEREDITY 



arities of individuals and classes deserve to be regarded as 

 innate. Since individuals have only one life each, we cannot 

 test our theories by rearing the same people first in one 

 environment and then in another. But races have sometimes 

 changed their mental environments very rapidly. Under 

 these conditions whatever psychical alterations occur must be 

 considered, not as innate, but as acquired. 



