DIVERGENT EVOLUTION THROUGH SEGREGATION. 297 
the same situation is maintained by a loss of migrational power as soon 
as the germs begin to develop. In these lower organisms it is evident 
that the success of the individual must depend on its physiological 
rather than its psychological adaptations; and if an initial divergence 
of adaptations results in a slight difference in the kinds that sueceed in 
germinating in contrasted situations, the difference is directly due to a 
diversity in the forms of natural selection affecting the seed, and the 
separation is what I hereafter describe as local separation, passing into 
local segregation. We therefore see that what I here call industrial 
segregation depends on psychological powers acting in aid of divergent 
physiological adaptations to the environment, or in aid of adaptations 
that are put to different uses. 
Observation shows that there is a multitude of cases in which en- 
deavor according to endowment brings together those similarly endowed 
and causes them to breed together; and when the species is thus divided 
into two or more groups somewhat differently endowed, there will cer- 
tainly be an increased divergence in the offspring of the parents thus 
segregated; and so on in each successive generation, as long as the 
individuals find their places according to their endowments, and thus 
propagate with those similarly endowed, there will be accumulated 
divergence in the next generation. Indeed it is evident that endeavor, 
according to endowment, may produce under one environment what 
natural selection produces when aided by local separation in different 
environments. As it produces the separate breeding of a divergent 
form without involving the destruction of contrasted forms, it is often 
the direct cause of divergent transformations; while natural selection, 
which results in the separate breeding of the fitted through the failure 
of the unfitted, can never be the cause of divergence unless there are 
concurrent causes that produce both divergent forms of natural selec- 
tion and the separate breeding of the different kinds of variations thus 
selected. 
Suetudinal intension.—A nother law is usually believed to be connected 
with endeavor which, if it exists, must conspire to enhance its tendency 
to produce divergent evolution. I refer to the influence which the 
habitual endeavor of the parents has on the inherited powers of the off- 
spring. We may call it the law of endowment of offspring according to 
the exercise or endeavor of parents, or, more briefly, suetudinal intension. 
The inherited effects of use and disuse have been fully recognized by 
Darwin, Spencer, Cope, Murphy, and others, and need not here be dis- 
cussed. The one point to which I wish to call attention is, that in order 
that diversity of use should produce divergent evolution, it is necessary 
that free crossing should be prevented between the different sections of 
the species in which the diversity of use is found. Now this condition 
of separate breeding is often secured by industrial segregation. In 
other words, the law of endeavor, according to endowment, often se- 
cures separation according to endowment, and this gives an opportunity 
