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REV. J. T. GULICK ON DIVERGENT EVOLUTION 
but if, during its brief period of local divergence, Industrial 
or Chronal Segregation is introduced, the variety becomes 
more and more differentiated, and, as one after another the 
different forms of Reflexive Segregation arise, it passes into a 
well-defined species. There is, however, reason to believe that 
the order of events is often the reverse, Reflexive forms of 
Segregation being the cause of the first divergences. 
As Spatial Segregation does not depend upon diversity in the 
qualities and powers of the organism, so also it does not usually 
result in distributing the organism in different localities according 
to their differences of endowment. The causes that produce it 
are primarily separative, not segregative. 
Migration is produced by the natural powers of the organism, 
acting under the guidance of instincts that usually lead a group 
of individuals, capable of propagating the species, to migrate 
together ; while the organisms that are most dependent on 
activities in the environment for their distribution, are usually 
distributed in the form of seeds or germs, any one of which is 
capable of developing into a complete community. 
The causes of Separation between the different sections, and 
of Integration between the members of one section, are therefore 
sufficiently clear ; but what are the causes of difference of cha- 
racter in the different sections, especially when they are exposed 
to the same environment? These causes all come under what I 
call Intensive Segregation, which, for the sake of saving repetition , 
will be fully discussed in a separate paper. 
( d ) 9. Eertilizational Segregation. 
Since writing this chapter on Environal Segregation, I have 
seen Francis Gfalton’s short article on “ The Origin of Varieties ” 
published in ‘Nature,’ vol. xxxiv. p. 395, in which he refers to a 
cause of segregation that had not occurred to me. He says : — “ If 
insects visited promiscuously the flowers of a variety and those 
of the parent stock, then — supposing the organs of repro- 
duction and the period of flowering to be alike in both, aud 
that hybrids between them could be produced by artificial cross- 
fertilization — we should expect to find hybrids in abundance 
whenever members of the variety and those of the original stock 
occupied the same or closely contiguous districts. It is hard to 
account for our not doing so, except on the supposition that insects 
feel repugnance to visitiug the plants interchangeabty.” 
