6 HEREDITY AND ENVIRONMENT 



race improvement can compare for thorough- 

 ness, permanence of effect, and certainty of 

 results, with that which attempts to change 

 the natures of men and to establish in the blood 

 the qualities which are desired. We hear 

 much nowadays about man's control over na- 

 ture, though in no single instance has man 

 ever changed any law or principle of nature. 

 What man can do is to put himself into such 

 relations to natural phenomena that he may 

 profit by them, and all that can be done to- 

 ward the improvement of the human race is to 

 apply consciously to man those great princi- 

 ples of development and evolution which have 

 been operating unknown to man through all 

 the ages. 



A. PHENOMENA OF DEVELOPMENT 



One of the greatest and most far-reaching 

 themes which have ever occupied the minds of 

 men is the problem of development. Whether 

 it be the development of an animal from an 

 egg, of a race or species from a pre-existing 

 one, or of the body, mind and institutions of 

 man, this problem is everywhere much the 



