INTERACTION OF THE FOUR PRINCIPLES OF SEGREGATION. 55 
here proposed it is made to cover superior influence over the acquired 
characters of associates, whether the community consists of rational 
. beings or not. A similar objection has often been urged against the 
use of ‘‘selection’’ in the Darwinian sense; but, on the whole, no 
better word has been found to designate the gaining of a full share in 
the propagation of the next generation, and so a full share of influence 
on the inherited characters of the community, whether it be by win- 
ning the interest of the rational part of the environment or by secur- 
ing adaptation to other conditions in the environment. Each new 
term is an innovation, and like all innovations must prove its useful- 
ness before it can prevail or be elected. 
III. INTERACTION OF THE FOUR PRINCIPLES OF SEGREGATION. 
1. Increased Effects Produced by the Repeated Action of One Principle or the 
Combined Action of More than One. 
Mr. Headley says that, in my terms ‘“‘intensive segregation” and 
‘‘cumulative segregation” the words ‘‘intensive’’ and ‘‘cumulative”’ 
are ‘‘misapplied.’”’ (See Problems of Evolution, p. 178.) I think his 
criticism is chiefly due to his having failed to note the definitions I 
have given to the terms and the way in which I have applied them. 
Intensive segregation I have described as due to natural selection and 
the other principles, producing transformation when coéperating with 
isolation.* Cumulative segregation is due to a succession of isolations 
coming at long intervals, in which each isolation opens the way for 
the formation of some new habit shaping the method of dealing with 
the environment, and, therefore, leads to the formation of a divergent 
species. For example, if a variable species of snails, having but little 
opportunity for transportation beyond the limits of the valley it in- 
habits, and no power for migration beyond the same, finds its habitat in 
the groves at one end of the chief mountain range of the island of Oahu, 
it may become well adapted to the conditions before a branch colony 
is planted in the next valley. Though the vegetation is the same in 
the two valleys, the new colony may be started by a single individual, 
whose habits lead it to prefer, for food and shade, some species of 
plant that is but little used by the mother colony, and thus divergent 
forms of endonomic selection shape the two colonies into two species. 
After many years the transportation of an individual from the second 
colony may result in the planting of a third colony with still further 
divergent habits; and so on till the valleys at the opposite end of the 
mountain range have become the habitat of species very closely re- 
* See Appendix I, Section VII, 3; also Appendix II, Section I, 8. 
