PREFACE. V 



types of spiritual life in man, present activities entirely unknown in 

 the inorganic world. In the degrees of attainment reached in coope- 

 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 well as 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 189 1. 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 



