214 
REV. J. T. GULICK ON DIVERGENT EVOLUTION 
tlie progenitors of man were deprived of their hairy coat by 
Sexual Selection that was, in its earlier stages, disadvantageous. 
It is therefore evident that the simple fact of divergence in 
any case is not a sufficient ground for assuming that the divergent 
form has an advantage over the type from which it diverges. We 
may, however, be sure that there is some cause or combination of 
causes that facilitates the intergenerating of those similarly 
endowed, and hinders their crossing with other kinds ; and if we 
can discover the cause of this Segregate G-eneration, we shall 
have an explanation of one part of the process by which the 
forms thus endowed are becoming a distinct race. 
Separation and Segregation with the Principle 
oe Intension. 
It will contribute to clearness in our discussion if we can gain 
definite conceptions of the conditions that are necessarily in- 
volved in Separate and Segregate Breeding. 
Separate Generation, which for convenience I call Separation, 
implies : — 
1st. The indiscriminate separation of the members of a species 
into different sections that are prevented from freely crossing 
with each other. 
2nd The aggregation of the members of one section ; that is, 
their being brought into conditions of time and place that allow 
of their freely crossing. 
3rd. The integration of the members of each section into one 
intergenerating group, through the operation of functional adap- 
tations by which the members of each section freely cross with 
each other. This analysis of the process shows that it may 
depend upon a great variety of causes, working together in a 
very complex way. We shall hereafter find, that the causes of 
separation may operate in such a way that no aggregation or 
propagation takes place amongst the members that are separated 
from the old stock ; but in such cases there is no Separate 
Generation, and therefore no Separation in the sense in which I 
use the word. 
Segregate Generation also consists of separation, aggregation, 
and integration; but it differs from Separate Generation in that 
in the latter the separation is indiscriminate, while in the former 
there is a more or less pronounced bringing together of those 
that are similarly endowed, with separation of those that are 
