PRE PAGE: 
In the present volume I have brought together in one connected 
presentation the chief results of my investigations concerning the 
factors of organic evolution. Portions of my theory of divergence 
which were published in the Linnean Society’s Journal are repro- 
duced in the Appendix, with careful revision; but the fullest exposi- 
tion of the fact that all evolution, as we now observe it, is divergent, 
and that other factors besides natural selection are absolutely neces- 
sary both for the origin and the continuance of this divergence, is 
given in the new chapters constituting the body of the volume. 
These chapters have been written while considering the most recent 
biological investigations bearing on the general theory of segregation. 
The first four chapters of the volume are introductory, in that they 
present many facts of divergence and distribution in both natural and 
domestic species, which remain complete enigmas till the forms of 
racial and habitudinal segregation have been fully recognized. Chap- 
ters V, VI, and VII present the fundamental laws of segregation, and 
the interaction between the different classes of factors—between 
isolation and selection, between racial segregation and habitudinal 
segregation, between autonomic factors and heteronomic factors. 
In Chapter VI, § II, 14-17 (pp. 101-111), will be found a fuller ex posi- 
tion than has been presented, in any of my essays published by the 
Linnean Society, of the tendency of certain combinations of partially 
segregative endowments to become more intense in successive genera - 
tions. Itis shown that this is especially the case when endowments, 
tending toward the mating of like forms with each other, are reinforced 
by varying degrees of mutualinfertility and incompatibility between 
unlike forms. Appendix II, $ IV, 3 (pp. 241-243), briefly indicates 
several methods of constructing what I have called the permutation 
triangle. It was first constructed in order to show that the sterility of 
cross-unions between divergent forms (whether they be varieties, 
species, genera, or higher groups), would lead rapidly to the extinction 
of most of these forms, if instincts and other endowments did not 
facilitate the union of compatible forms. The table thus constructed 
is found to be a concise presentation of certain classes of probabilities 
that arise in the pairing of things by chance. 
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