PREFACE 
This book has been prepared to meet a specific demand, long 
felt here and elsewhere, for an account of the various phases of evolu- 
tionary biology condensed within the scope of one volume of moderate 
size. The present writer has now for sixteen successive years pre- 
sented in lecture form to large classes of students the subjects of 
evolution, genetics, and eugenics. Never have we been able to find 
a single book that would cover the required ground. In fact it has 
been necessary to require, or at least to recommend, as many as 
three books. It is believed that the present book will furnish ade- 
quate reading material for a major or a semester course in evolutionary 
biology. Some supplementary reading may be necessary in case an 
instructor wishes to emphasize one or more phases of the subject; 
but for a first course in the subject we believe that all of the essential 
reading material will be found within the text itself. 
An effort has been made to present the subject in the best peda- 
gogical order. After a general introduction, a rather long chapter 
appears in which the whole history of the development of evolution- 
ary science is outlined, together with the names and contributions 
of the leading evolutionists. Part II is a presentation of the evi- 
dences of organic evolution, beginning with the bodies of evidence 
most definite and direct, and ending with the less definite and 
more controversial. Part III deals with causo-mechanical theories of 
evolution with Darwinism as the central topic. Part IV concerns 
itself with genetics or modern experimental evolution, and Part V 
with eugenics, or genetics as applied to human improvement. 
The book consists largely of excerpts, some long and some short, 
from both the older classical evolutionary writers and the modern 
writers. Our aim has been to select the most significant or character- 
istic passages from each author. In most cases this ideal has been 
attained, but it has sometimes happened that we have had to make 
our selection of material to meet a real need in the book, and accord- 
ingly have selected from an author a passage he himself might not 
consider particularly characteristic of his work. We have succeeded, 
nevertheless, in welding together out of a collection of isolated chapters 
and passages what seems to us to be a close approach to a coherent 
unit. Unification has been accomplished by the aid of editorial 
connecting passages, introductory statements, criticisms, and sum- 
maries. In certain cases it became necessary, for a variety of reasons, 
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