THROUGH CUMULATIVE SEGREGATION. 
197 
attributed to any lack of appreciation of what has already been 
accomplished. The propounders of a doctrine which has pro- 
foundly influenced every department of modern thought need no 
praise from me ; but as their theory is confessedly incomplete, 
and as one of the leaders in the movement has called attention to 
the need of a rediscussion of the fundamental factors of evolution, 
I offer my suggestions and amendments after prolonged and 
careful study. 
Physiological Selection and Segregate Fecundity . 
The abstract of Mr. Romanes’s paper on “ Physiological Selec- 
tion,” given in ‘ Nature’ August 5th, 12th, and 19th, 1886, did 
not come into my hands till the following January, when my 
theory of Divergent Evolution through Cumulative Segregation, 
which had been gradually developing since the publication of my 
paper on “ Diversity of Evolution under One Set of External 
Conditions,” was for the most part written out in its present 
form. Since then, and with reference to the discussion on 
Physiological Selection, I have worked out the algebraic formulas 
given in the last chapter, and have introduced exjdanations of 
the same ; but at the same time I have removed several chapters 
in which the principle of selection was discussed at length, and 
have endeavoured to bring the whole within a compass that 
would allow of its being published by some scientific society. 
In order to attain this end, I reserve for another occasion a dis- 
cussion of the principles of Intensive Segregation, under which 
name I class the different ways in which other principles com- 
bine with Segregation in producing Divergent Evolution. 
It was my intention to bring together examples of the differ- 
ent forms of Segregation discussed, that they might be pub- 
lished with the theoretical part ; but the large number of pages 
found necessary for even the briefest presentation of the prin- 
ciples involved, and the fact that Mr. Romanes’s paper has ap- 
peared relating to some of the same problems, leads me to present 
the results of my studies without further delay. The facts on 
which large portions of my theory rest are of the most familiar 
kind, and no additional light would be gained though their 
numbers wure multiplied a hundredfold. Indeed one of the 
marked features of my theory is that in its chief outlines it rests 
on facts that are universally acknowledged. The aim of the 
