THBOUGH CUMULATIVE SEGREGATION. 
273 
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. 
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. 
(b) Chronal Segregation. 
Cyclical. 
Seasonal. 
