PREFACE vii 



there encountered. Eugenics, on the other hand, deals 

 with the improvement of the human race under existing 

 conditions of law and sentiment. The Eugenist has to 

 take into account the religious and social beliefs and 

 prejudices of mankind. Other issues are involved be- 

 sides the purely biological one, though as time goes on 

 it is coming to be more clearly recognised that the 

 Eugenic ideal is sharply circumscribed by the facts of 

 heredity and variation, and by the laws which govern 

 the transmission of qualities in living things. What 

 these facts, what these laws are, in so far as we at 

 present know them, I have endeavoured to indicate in 

 the following pages ; for I feel convinced that if the 

 Eugenist is to achieve anything solid it is upon them 

 that he must primarily build. Little enough material, 

 it is true, exists at present, but that we now see to be 

 largely a question of time and means. Whatever be the 

 outcome, whatever the form of the structure which is 

 eventually to emerge, we owe it first of all to Mendel 

 that the foundations can be well and truly laid. 



R. C. P. 



Cambridge, March, 1911. 



