iv PREFACE. 



The principles molding segregation, and so controlling variation 

 and heredity, and the effects on racial and social evolution produced 

 by such control, are presented with considerable fullness of illustra- 

 tion on the biological side. For my purpose it did not seem necessary 

 to dwell at equal length on the social aspects. 



Another broad department of the subject is referred to in only the 

 briefest way. This is the effect of amalgamation or regressive segrega- 

 tion, both racial and social. I have, however, pointed out that in the 

 history of man segregation was the leading factor through countless 

 generations when races, languages, and institutions were becoming 

 increasingly subdivided ; and that it is only in modern times that the 

 barriers to free intercourse have been so rapidly yielding that regres- 

 sive segregation has been the predominant feature in human history. 



I have presented evidence that, even in the case of invertebrate 

 animals, members of the same species, exposed to the same environ- 

 ment in isolated groups, will often arrive at divergent methods of 

 dealing with the environment, and so subject themselves to divergent 

 forms of selection. If my contention is in accord with the facts, the 

 assumption which w r e often meet that change in the organism is 

 controlled in all its details by change in the environment, and that, 

 therefore, human progress is ruled by an external fate, is certainly 

 contrary to fact. 



It is of no little interest that the recent developments of biological 

 science, in both Europe and America, are pointing, not only to the 

 power of the organism to deal with the same environment in different 

 ways, and so to determine the forms of what I have called active (or 

 cndonomic) selection, but also the power of many animals to deal with 

 sudden changes in the environment in such a way that the group is 

 saved from extinction till "coincident variations" have time to arise, 

 insuring completer adaptation to the new conditions through selection. 

 The teachings of biology are thus coming more nearly into accord 

 with that school of sociology which has for years maintained that the 

 social group may learn to determine the form of its own social evolu- 

 tion. We are thus led to hope that man will in time determine his 

 own evolution, racial as well as social ; for when sufficiently advanced 

 to realize the breadth of the responsibilities resting upon him, the 

 form of his racial inheritance will naturally be determined by the 

 ideals shaping his social organization. 



In the third chapter, and again near the end of the last chapter, 

 attention is called to the fact that, in accommodational and anticipa- 

 tory action, and in cooperation for the attainment of future results, 

 all forms of life, from the earliest protozoa till we reach the highest 



