296 DIVERGENT EVOLUTION THROUGH SEGREGATION. 
The different forms of industrial segregation are sustentational, pro- 
tectional, and nidificational segregation. 
For the production of industrial segregation it is necessary that there 
should be, in the same environment, a diversity of fully and of approx- 
imately available resources more or less Separated from each other, 
and in the organism some diversity of adaptation to these resources, 
accompanied by powers of search and of discrimination, by which it is 
able to find the resources for which it is best fitted and to adhere to 
the same when found. 
The relation in which these causes stand to each other and through 
which they produce segregation may be described as separation accord- 
ing to endowment—produced by endeavor according to endowment. 
It is evident that if initial variation presents in any case a diversity 
of adaptations to surrounding resources that can not be followed with 
out separating those differently endowed, we shall have, in the very 
nature of such variation, a cause of segregation and of divergent evo- 
lution. Some slight variation in the digestive powers of a few indi- 
viduals makes it possible for them to live exclusively on some abundant 
form of food, which the species has heretofore only occasionally tasted. 
In the pressure for food that arises in a crowed community these take 
up their permanent abode where the new form of food is most accessible, 
and thus separate themselves from the original form of the species. 
These similarly endowed forms will therefore breed together, and the 
offspring will, according to the law of diversity through segregation, be 
still better adapted to the new form of food. And this increasing 
adaptation, with increasing divergence, might continue for many gen- 
erations, though every individual should come to maturity and propa- 
gate; that is, though there were no enhancing of the effect through 
diversity of selection, or indeed through any other cause producing 
intensive segregation. And when different forms of intention do arise 
they may be entirely independent of change in the environment, the 
only change being in the forms or functions of the organism. 
In choosing a name for this form of segregation I first thought of 
calling it physiological or functional segregation; but such a name is, 
on closer examination, found toimply both too much and too little; for, 
on the one hand there is probably no form of segregation that is not in 
some way or in some degree due to physiological or functional causes, 
and on the other hand this special form of segregation is as dependent 
on psychological causes which guide the organism in finding and in 
adhering to the situation for which it is best fitted, as it ison the initial 
divergence of the more strictly physiological adaptations by which it is 
able to appropriate and assimilate the peculiar form of resource. In 
the case of freely-moving animals the psychological guidance is an 
essential factor in the success of the individual; while in the case of 
plants and low types of animal life, the suitable situation is reached by 
a wide distribution of a vast number of seeds, spores, or germs, and 
