24G 
REV. J. T. GTJLICK ON DIVERGENT EVOLUTION 
in connection with different forma of partial Segregation will 
now be considered. 
17, 18. Segregate Fecundity and Segregate Vigour . — By Segre- 
gate Fecundity I mean neither Segregation produced by Fecun- 
dity nor Fecundity produced by Segregation, but the relation in 
which species or varieties stand to each other when the intergen- 
eration of members of the same species or variety results in 
higher fertility than the crossing of different species or varieties. 
In like manner Segregate Vigour is the relation in which species 
or varieties stand to each other when the intergeneration of 
members of the same species or variety produces offspring more 
vigorous than those produced by crossing with other species or 
varieties. Integrate Fecundity and Integrate Vigour are the 
terms by which I indicate the relation to each other of forms in 
which the highest fertility and vigour are produced by crossing, 
and not by independent generation. 
Before discussing these principles through which the influence 
of Segregation is greatly increased, it will be an advantage if we 
can gain some idea of the nature of Cumulative Fertility in its 
relations to a law of still wider import. I refer to the fourfold law 
of antagonistic increase and mutual limitation between (1) In- 
tegration, (2) Segregation, (8) Adaptation, (4) Multiplication — 
in other words between (1) General invigoration and power of 
variation through crossing, (2) The opening of new opportunities 
and independent possibilities, (3) Special adaptation to present 
circumstances, (4) Powers of multiplied individualization. Darwin 
has considered at length the 1st and the 3rd, though I do not 
remember that he has anywhere pointed out that their develop- 
ment is due to a kind of self-augmentation. I believe this is so 
emphatically the case that the former might well be called the 
law of Self-Cumulative Vigour, and the latter the law of Self- 
Cumulative Adaptation. Corresponding to these two laws, I 
find the additional laws of Self- Cumulative Segregation and Self- 
Cumulative Fertility. Darwin’s theory, that Diversity of Natural 
Selection is directly and necessarily dependent on exposure to 
different external conditions, tends to obscure, though not to 
deny, the fact that the breeding together of the better adapted, 
which causes the increase of adaptation, is due to the different 
degrees of endowment in the organism, rather than to diversity 
in the environment. It is also true of segregative endowment 
and of fertility that they are necessarily cumulative whenever 
