THROUGH CTJMIJLATIVE 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 Fecunditg. 



The abstract of Mr. Eomanes'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 explanations 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 diff"erent 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. Eomanes'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 tlie most familiar 

 kind, and no additional light would be gained though their 

 numbers were 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 



