212 REV. J. T. GULTCK ON DIVERGENT EVOLUTION 
possessing low powers and small opportunities for migration 
divide the same area, or an area no larger, between many re- 
presentative species, shows that independent generation is an 
important element in their divergence. 
CHAPTER II. 
Cumulative Divergence through Cumulative Segregation. 
Local separation in dissimilar environments is the only cause 
of Segregation that has been clearly pointed out by Darwin. I 
shall, however, endeavour to show that there are other causes 
producing Segregation, and that, without any Change of En- 
vironment or change in the Environment, they may produce 
all the phenomena of Divergent Evolution. Any cause that, 
out of two or more kinds of successful variations, brings to- 
gether one kind in such a way as to facilitate their breeding 
together, or to hinder their breeding with those of other kinds, 
is according to my definition a cause of Segregate Breeding ; 
and the experience of breeders shows that wherever such causes 
operate divergent evolution is the result, and that the diver- 
gence accumulates when the process is continued through many 
generations. From their experiments we learn that any form 
of Segregate Breeding persistently continued will result in diver- 
gent evolution. As any form of natural selection in which 
other than typical forms have the advantage will result in Mono- 
typic Evolution, so any form of segregate generation will produce 
Polytypic Evolution. I call this the law of Cumulative Diver- 
gence through Cumulative Segregation. It is a generalization 
established by the widest experience of mankind in the cultiva- 
tion of plants and the breeding of animals ; and any assumption 
that is not in accord with it may be wisely called in question. 
I, therefore, judge that the advantage or disadvantage of their 
divergence, to individuals diverging from the typical form of a 
species, cannot be the factor that determines whether the diver- 
gence shall be accumulated. 
A divergent member of any intergenerating group cannot long 
perpetuate its kind, if the divergence is any disadvantage ; for 
the superior propagation of the more successful kinds will soon 
overpower the influence of the less successful; and the result 
will be Monotypic Evolution. The case is, however, very dif- 
ferent with variations that are wholly or partially separated from 
