RECENT PROGRESS 
IN THE STUDY OF VARIATION, 
HEREDITY, AND EVOLUTION 
CHAPTER I 
INTRODUCTION 
THE present volume deals with variation and inheri- 
tance in plants and animals, especially in so far as 
those subjects bear upon the problem of the origin of 
species. By inheritance we mean those methods and 
processes by which the constitution and characteristics 
of an animal or plant are handed on to its offspring, 
this transmission of characters being, of course, asso- 
ciated with the fact that the offspring is developed by 
the processes of growth out of a small fragment de- 
tached from the parent organism. The term ‘ varia- 
tion,’ on the other hand, includes a number of different 
phenomena which will be described at greater length 
as the work proceeds ; but; broadly speaking, we may 
say that the study of variation is concerned with the 
circumstance that members of the same species are 
not all alike, and more particularly with the fact that 
I 
