Social Environment and Eugenics 85 



mass of statistical evidence that has been 

 worked out with scientific precision in support 

 of the influence of heredity. This, he claims, 

 establishes his case. And on inspection it 

 proves that the evidence is such as to demand 

 attention. It includes some of the most valu- 

 able biological work of recent years, beginning 

 about 1900 with the rediscovery of the Men- 

 delian law of heredity and proceeding into a 

 veritable maze of data covering many phases 

 of the problem. Perhaps the most important 

 part of the evidence as bearing upon the ques- 

 tion before us is that connected with the bio- 

 metrical study of heredity, the beginnings of 

 which go as far back as Galton, who may be 

 regarded as the founder of the method.^ The 

 biometricians have adapted the theory of sta- 

 tistics to their field of work with great success. 

 The most important of the mathematical oper- 

 ations that they have developed and used is the 

 computing of the so-called coefficient of corre- 

 lation — a means of finding precisely the extent 

 of agreement existing between two sets of re- 

 lated data. With the aid of this mathematical 

 tool it has been found possible to measure, far 



1 Doncaster, L., Heredity in the Light of Recent Re- 

 search, Ch. IV. G. P. Putnam's Sons, New York, 1911. 



