PREFACE ix 



students is the establishing of law and order among 

 the phenomena 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 besides 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 191 1. 



