214 



REV. J. T. GTJLICK ON DIYERGENT EVOLUTIOJf 



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 

 OF 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 G-eneration, 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 

 G-eneration, 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 



