236 
REV. J. T. GULICK ON DIVERGENT EVOLUTION 
vast and complex environment ; and the former is secured by the 
advantage over rivals possessed by the variations that favour 
crossing, and the latter hv the better escape from the swamping 
effect, and sometimes from the competition of certain rivals, 
secured by the more segregative variations. TVe must there- 
fore believe that, whenever in the history of an organism there 
arise segregative variations which are able to secure sufficient 
sustentation and propagation to continue the species, the segre- 
gative quality of the forms thus endowed will be preserved and 
accumulated through the self-accumulating effect of the segre- 
gative endowments. 
It is probable that in many of the higher vertebrates sexual 
instincts tend to bring together those of somewhat divergent 
character, but the difference preferred is within very narrow 
limits ; and beyond those limits, it may be said that the general 
law for sexual attraction is, that it varies inversely as the dif- 
ference in the characters of the races represented, if not inversely 
as some power of such difference. The action of such a law 
is necessarily segregative, whenever the divergence has, through 
other causes, passed beyond the limit of higher attraction. Before 
Sexual Segregation can arise, there must arise distinctive charac- 
teristics by means of which the members of any section may 
discriminate between those of their own and other sections. If 
there are no constant characteristics, there can be no constant 
aversion between members of different groups, no constant pre- 
ference of those of one’s own group. Erom this it follows, that 
before Sexual Segregation can arise, some form of Segregation 
that is not dependent on accumulated divergence of character 
must have produced the divergence on which the Sexual Segre- 
gation depends. Such forms are Local, Social, and some hinds of 
Industrial Segregation. When varieties have arisen through 
these causes, it often happens that Sexual Segregation comes in 
and perpetuates the Segregation which the initial causes can no 
longer sustain. As long as the groups are held apart by diver- 
gent sexual instincts, it is evident that divergent forms of Sexual 
Selection are almost sure to arise, leading to a further accumu- 
lation of the divergence initiated by the previous causes. 
If there is any persistent cause by which local and social 
groups are broken up and promiscuously intermingled before 
recognizable characters are gained, the entrance of Sexual Segre- 
gation will be prevented. I therefore conclude that the chief 
