PREFACE 



such vast importance to mankind as the knowl- 

 edge of and the control over heredity and 

 development. Within recent years the experi- 

 mental study of heredity and development has 

 led to a new epoch in our knowledge of these 

 subjects, and it does not seem unreasonable to 

 suppose that in time it will produce a better 

 breed of men. 



The lectures which compose this volume were 

 given at Northwestern University in February, 

 1914, on the Norman W. Harris Foundation 

 and were afterward repeated at Princeton Uni- 

 versity. I gladly take this opportunity of ex- 

 pressing to the faculties, students and friends 

 of both institutions my deep appreciation of 

 their interest and courtesy. In attempting to 

 present to a general audience the results of re- 

 cent studies on heredity and development, with 

 special reference to their application to man, 

 the author has had to choose between simplicity 

 and sufficiency of statement, between apparent 

 dogmatism and scientific caution, between a 

 popular and a scientific presentation. These 

 are hard alternatives, but the first duty of a 

 lecturer is to address his audience and to make 



