PREFACE 
THE present volume is the outgrowth of a course of lectures 
on Eugenics which has been given for several years in the Univer- 
sity of California. Its aim is to present an account of the various 
forces which are at present modifying the inherited qualities of 
civilized mankind. In dealing with so extensive and complex 
a subject I have doubtless committed a number of errors and have 
probably not altogether escaped from being misled by statistical 
fallacies into which I have so often accused others of having 
fallen. The more extensively I have delved into the varied 
literature on the biological evolution of man, the more I have 
become impressed with the necessity of employing extreme cau- 
tion in drawing conclusions. Few subjects, in fact, present so 
many pitfalls for the unwary. It is with the conviction that it is 
especially important in this field to be sure one is right before 
going ahead that I have devoted so much effort to critical analysis 
at the risk of becoming tedious to the general reader. 
I am indebted to my colleagues Professor F. B. Sumner and 
Professor F. J. Teggart for reading my original manuscript and 
for making a number of valuable suggestions. 
The preparation of the present work has involved the compila- 
tion of an extensive bibliography which is to be published as an 
additional volume so that the references may be rendered avail- 
able for other investigators. 
S. J Hormes 
Berkeley, Calif. 
Jan. 1921. 
