THROUGH CUMULATIVE SEGREGATION. 



273 



or less, and that whatever causes a greater difference in two 

 sections that are prevented from intergenerating will also be a 

 giuse of increased Segregation. 



It has been observed that some of the causes enumerated in 

 this and the previous 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 co-operate in securing a given division 

 of a species, and one form is superimposed upon another, the 

 aggregate effect must be incalculably great ; but we easily per- 

 ceive that it may be indefinitely enhanced by causes producing 

 increased divergence in the segregated branches. The causes 

 which produce monotypic evolution when associated with Inter- 

 generation must be equally effective in producing polytypic 

 evolution when associated with Segeneration, whether in its 

 separative or segregative forms. But the discussion of Intensive 

 Segregation must be reserved for another occasion. 



Believing that the study of Cumulative Segregation in its re- 

 lations to the other factors of evolution will throw light on the 

 origin of species far beyond what I have been able to elicit, I trust 

 the subject will secure the attention of those who enjoy better 

 opportunities than I do for carrying forward such investigations. 



26 Concession, Osaka, Japan, 

 May 12, 1887. 



Appendix. 

 Classified Table of Forms of Segregation. 

 A. 



Environal Segregation. 



{a) Industrial Segregation. 

 Sustentational. 

 Defensive. 

 Nidificational. 

 (1)) Chronal Segregation. 

 Cyclical. 

 Seasonal. 



