294 DIVERGENT EVOLUTION THROUGH SEGREGATION. 
Now, as we have just pointed out, we know from the fundamental 
laws of the organic world, that cumulative segregation of this kind 
must produce cumulative divergence of types. 
The segregation that resuits from the natural causes enumerated in 
this paper is cumulative in two respects. In the first place, every new 
form of segregation that now appears depends on, and is superimposed 
upon, forms of segregation that have been previously induced; for 
when negative segregation arises, and the varieties of a species be- 
come less and less fertile with each other, the complete infertility that 
has existed between them and some other species does not disappear, 
nor does the positive segregation (that is, the prevention of the con- 
sorting of the species characterized by this mutual incapacity) cease. 
The means by which the males and females of one species find each 
other are not abrogated when the species falls into segregated varie- 
ties. In the second place, whenever segregation is directly produced 
by some quality of the organism, variations that possess the endow- 
ment ina superior degree will have a larger share in producing the 
segregated forms of the next generation, and accordingly the segrega- 
tive endowment of the next generation will be greater than that of the 
present generation; and so with each successive generation the segre- 
gation will become increasingly complete. 
The principle of cumulative segregation, first in its independent 
action, and still further when combined with the different principles 
by which the divergence of the segregated branches is intensified, gives 
a formal explanation of the ever-expanding diversities of the organic 
world. It shows how varieties arise and pass into species, how species 
pass into genera, genera into families, families into orders, and orders 
into classes and the higher divisions, as far as evolution by descent 
extends. It brings to light the dependence of this whole process on 
the influences that produce segregation; and shows how these influ- 
ences, added to variation, heredity, and the other acknowledged powers 
residing in organisms, must produce the phenomena of divergent evo- 
lution. 
COMPETITIVE DISRUPTION. 
3efore entering upon the discussion of the direct causes of cumula- 
tive segregation, let us briefly consider a law resulting from the compe- 
tition 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 segrega- 
tion and divergent evolution. It is manifest that competition for iden- 
tical resources and geographical segregation are conditions which can 
not exist at the same time between the same members of any species; 
but it is also manifest that when there are no natural barriers separ- 
ating the different districts of an area, part of which is occupied by a 
species, pressure for food through a great increase in the population 
