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REV. J. T. GULICK ON DIVERGENT EVOLUTION 
such a way as to ensure increasing divergence in each successive 
generation, as long as the individuals of the two groups are kept 
from intergenerating. In my paper on Diversity of Evolution 
under one Set of External Conditions , I spoke of this principle of 
divergence as “ Separation with Variation;” but in order to dis- 
tinguish the antecedent condition, which is Separation, from the 
result, which is something more than Variation, I now call the 
certainty that some form of divergent transformation will arise 
when intergeueration is prevented the principle of Intension • 
and Segregation produced by independent transformation I call 
Intensive Segregation. 
As Separate and Segregate Generation are so closely related, 
I have, in order to avoid a multiplication of terms, classified the 
two principles together under the general term Segregation. In 
my discussion of the causes of Segregation I shall, however, 
endeavour to determine concerning each class of causes whether 
they are primarily Separative or Segregative. 
A full discussion of the causes of Segregation would require 
that under each combination of causes to which we give a dis- 
tinctive name we should show : — 
1. How the Independent Generation is produced. 
2. How the difference of character in the different sections is 
produced. 
3. How the aggregation in place bringing together the members 
of each section is produced. 
4. How the correspondence in times and seasons necessary for 
intergeneration is secured within each section. 
5. How the correspondence of community and of Sexual and 
Social instincts necessary for intergeneration is secured within 
each section. 
6. How the correspondence in structure, in dimensions, and 
in the mutual potentiality of the sexual elements necessary for 
intergeneration is secured within each section. 
It will, however, be observed that, with the exception of the 
two first, these questions relate to the necessary conditions that 
must always exist in the case of every iutergenerating group ; 
and as it is evident that intergeneration in some degree must be 
the normal condition in every sexual, that is in every gamo- 
genetic, species, we may here assume that all the conditions 
necessary to intergeneration exist, except so far as they have 
been disturbed by causes producing Segeneration. In tracing 
