THROUGH CUMULATIVE SEGREGATION. 
221 
Competitive Disruption. 
Before entering upon the discussion of the direct causes of 
Cumulative Segregation, let us briefly consider a law resulting 
from the competition of kindred with each other, which brings to 
light the fact that such competition is one of the most important 
factors in preparing the way for, and in giving intensity to, the 
activities that lead to Segregation and divergent evolution. It 
is manifest that competition for identical resources and Greogra- 
phical Segregation are conditions which cannot exist at the same 
time between the same members of any species; but it is also 
manifest that, when there are no natural barriers separating the 
different districts of an area part of which is occupied by a 
species, pressure for food through a great increase in the popu- 
lation will tend to distribute the species over the whole area ; 
and, if the available resources in the different districts are consi- 
derably diverse, the overflow of population from the crowded 
district will be subjected to a necessary change of habits ; and 
thus, through competition, there will be the disruption of old 
relations to the environment, and the bringing in of conditions 
that give the highest efficiency and the fullest opportunity to all 
the activities that produce Segregation. In the case of animals, 
no condition can tend more strongly to produce migration than 
scarcity of food in the old habitat ; and in the case of both plants 
and animals, a great increase in the numbers that are exposed to 
the winds, currents, and other transporting influences of the 
environment increases the probability that individuals will be 
carried to new districts where circumstances will allow of their 
multiplying, and where they will, at the same time, be prevented 
from crossing with the original stock. In many cases the segre- 
gation thus brought about ivill be in districts where the environ- 
ment is the same, and in other cases the pressure for food or 
other resources will lead portions of the species to take up new 
habits in the effort to appropriate resources not previously used ; 
and through these new habits they will often be segregated from 
those maintaining the original habits. I shall hereafter show 
that in both these cases there is a tendency to divergent 
evolution. 
I at one time thought of describing this principle as a form 
of Segregation, calling it clominational segregation ; but fuller 
reflection convinces me that the domination of the strong over 
LINN. JOURN. — ZOOLOGY, YOL. XX. IS 
