THROUGH CUMULATIVE SEGREGATION. 
215 
dissimilar. Segregate Generation is therefore the separation of 
dissimilars, with the aggregation and integration of similars. As 
we have already seen, Segregate Breeding may be produced by 
Separate Breeding accompanied by Diversity of Natural Selection 
in the different sections. It is also evident that any other cause 
that develops in one or more of the separate sections of the 
species characters that are not found in the other sections will 
produce Segregate Breeding. Such cases are Diversity of Selec- 
tion of other forms than Natural Selection, Diversity in the 
inherited effects of Use and Disuse (unless physiologists have 
been mistaken in supposing that there are any such effects), and 
Diversity in the inherited characters derived from the Direct 
Effects of the Environment (unless, again, Weismann is right and 
the general belief wrong). Segregate Breeding may, moreover, 
be produced directly by the very way in which the separation of 
the different sections is secured. One of the best examples of 
this kind of Segregation is seen in what I call Industrial Segre- 
gation, wdiere the members of a species are distributed according 
to their endowments, those of similar endowments being brought 
together. In such cases, Segregation is introduced as soon as 
the Sepai’ation, without depending on the subsequent action of 
the environment, or on diverse forms of Use, or of Selection ; 
though there can be no doubt that, in the great majority of 
cases, Diversity of Use and Diversity of Selection of some kind 
will in time come in to intensify the result. 
There is another invariable sequence which it is necessary we 
should keep in mind, if we would understand the relation in 
which these two principles stand to each other. I refer to the 
certainty that all prolonged Separate Breeding will be trans- 
formed into Segregate Breeding. In other words, indiscriminate 
separation, in which there is no apparent difference in the dif- 
ferent groups, is in time found to be a separation in which there 
is a decided difference in the different groups. Whenever a 
sufficient number of the same species to ensure propagation are 
brought together in an isolated position, Separate Generation is 
the result ; and, if this Separate Generation is long-continued, 
we have reason to believe, it always passes into Segregate Genera- 
tion with divergent evolution. The fundamental cause for this 
seems to lie in the fact that no two portions of a species possess 
exactly the same average character, and that the initial differences 
are for ever reacting on the environment and on each other in 
