PREFACE. Vv 
types of spiritual life in man, present activities entirely unknown in 
the inorganic world. In the degrees of attainment reached in codpe- 
rative action (with the division of labor and community of interest), 
and in anticipatory and discriminative action (securing adaptation 
to future conditions), we find a definite test of the stages of evolution 
reached—a test that is applicable to the lowest as wellas to the highest 
living creatures. 
Of my papers previously published, the one on Divergent Evolution 
has received the most attention. This is perhaps due to the fact that 
it was not only published in London in the Linnean Society’s Journal 
for 1887, but was reproduced in this country in the report of the 
Smithsonian Institution for 1891. I wish, however, to emphasize 
the importance of the factors enumerated and illustrated in the one 
on intensive segregation (see Appendix II). If we would fully com- 
prehend the factors producing the segregation of organic types, we 
must recognize not only the forms of isolation by which groups are 
first set apart; but also the physiological and psychological forms of 
segregation by which the slightly divergent forms are held perma- 
nently apart, and still further, the factors producing divergence in 
these isolated groups, and so resulting in intensive segregation. I 
show that intensive segregation is due not only to the exposure of 
isolated groups to different environments, but also to the different 
methods of dealing with the same environment adopted by the iso- 
lated groups. I also point out other factors that are subject to 
change without any change in the activities lying outside of the 
species; and all such I class as autonomic factors. Throughout all 
the chapters the underlying purpose has been the investigation of the 
autonomic as well as the heteronomic factors controlling evolution. 
The chief hindrance to the increase of our knowledge of the method 
of evolution is the tendency to regard some one of the several prin- 
ciples influencing segregation as the one principle controlling the 
whole process. I believe Prof. H. F. Osborn makes no mistake when 
he suggests that the ruling method of the next important advance in 
the interpretation of evolution must be one recognizing the complex 
action of diverse principles, and at the same time grasping the under- 
lying unity of the process. In the present volume the question is 
raised whether segregation, with its controlling influence in the 
spheres of both racial and habitudinal evolution, is not the underlying 
principle we are seeking. It must, however, be carefully noted that 
segregation as defined in this volume covers a much wider sphere 
than isolation. In order to reach the more pronounced results of 
racial segregation, the separate groups produced by isolation must 
