CHAPTER IX. 
SUMMARY AND CONCLUSION. 
I. SuMMaRY. 
1. Segregation. 
As segregate breeding is the fundamental principle producing racial 
segregations, and as isolation and selection codperate in controlling 
the degrees and forms of segregate breeding, and therefore in control- 
ling variation and heredity, so also it will be found that segregate 
association is the fundamental principle producing habitudinal segre- 
gation, and so partition and election coéperate in controlling the forms 
of segregate association, and therefore in controlling innovation and 
tradition. 
It is also evident that the initial racial segregation introduced by 
discriminate isolation, or by the indiscriminate isolation of a few pairs, 
may be greatly hastened and intensified by the exposure of the isolated 
groups to diverse forms of selection; and it is no less certain that, 
even when the environment is virtually the same, diverse forms of 
selection may be introduced by diverse methods of using the environ- 
ment that are liable to be adopted by the isolated groups. Moreover, 
it is equally evident that the initial habitudinal segregation intro- 
duced by discriminate partition, or by the indiscriminate partition of 
a single pair, may be greatly hastened and intensified by the exposure 
of the separated groups to diverse forms of election arising from the 
various forms of success, which are determined by the activities that 
become habitual in each group. 
The evolution of organic types is originated and maintained by 
partition and election producing habitudinal segregation, and by 
isolation and selection producing racial segregation. Without these 
principles producing their intensifying and ramifying effects on organic 
types, the complex world of life could never have arisen out of the 
simple forms of primitive life; and without the continuance of the 
segregations thus produced the diversity that has been reached would 
soon be dissolved and the whole world of life would be reduced to 
but one species. But the history of races and species shows, on the 
one hand, that segregate breeding when fully fortified by physiologi- 
cal and psychological incompatibilities is never removed; and, on the 
other hand, that whenever increasing stringency of segregate breed- 
ing is in any way introduced, there we have either the transforma- 
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