PRINCIPLES INTENSIFYING SEGREGATION. 175 



causes already considered. Segregation is not simply the indepen- 

 dent generation of different sections of a species, but the independent 

 generation of sections that differ. Though indiscriminate isolation of 

 a small section of a species may produce an initial difference, it is 

 evident that the degrees of difference may be greater or less, and that 

 whatever causes a greater difference in two sections that are prevented 

 from intergenerating will also be a cause of increased segregation, and 

 may be classed as a form of intensive segregation. 



It has been observed that some of the causes enumerated in this 

 chapter are primarily separative, and that no one of those that are 

 primarily segregative is at any one time segregative in regard to many 

 classes of characters. As several forms of segregation may cooperate 

 in securing a given division of a species, and one form is superimposed 

 upon another, the aggregate effect must be great ; but we easily 

 perceive that it may be indefinitely enhanced by causes producing 

 increased divergence in the segregated branches. The causes which 

 produce monotypic evolution when associated with intergeneration 

 must be equally effective in producing polytypic evolution when asso- 

 ciated with isolation whether in its separative or segregative forms. 

 But the discussion of intensive segregation must be reserved for 

 another occasion. 



A Lack in this First Classification of Segregative Principles. * 



The classification of segregative principles here given does not draw any clear 

 distinction between those resting upon acquired characters and habitudes and 

 those resting upon innate characters and aptitudes. For example, industrial 

 segregation is denned as "Segregation arising from the activities by which the 

 organism protects itself against adverse influences in the environment, or by 

 which it finds and appropriates special resources in the environment." Now it 

 is manifest that in some cases the different methods of using the environment may 

 be determined by acquired habitudes rather than by inherited aptitudes, and the 

 demarcation thus produced will, in the first place, be habitudinal, though in the 

 end it may result in racial demarcation. 



The interaction between the principles producing racial segregation and those 

 producing habitudinal segregation is discussed in Chapter V (pp. 45-78). 



It should also be noted that since this paper was brought before the Linnean 

 Society, isolation has come into general use for designating the prevention of free 

 crossing, by which the demarcation of racial groups is determined. This leaves 

 the term " segregation " more free to designate the combined action of the prin- 

 ciples producing the demarcation of groups and of those producing the intensifi- 

 cation of the characters of the separated groups: Partition and isolation pro- 

 duce habitudinal and racial demarcation, while election and selection produce 

 habitudinal and racial intensification, and the combined action of the four 

 principles produces segregation both racial and habitudinal. (For a fuller state- 

 ment see Chapters V and VI.) 



*As this explanation does not occur in the original paper it is printed in 

 different form. 



