470 
EECAPITULATION. 
Chap. XIV. 
view we can understand how it is that in each region 
where many species of a genus have been produced, 
and where they now flourish, these same species should 
present many varieties; for where the manufactory of 
species has been active, we might expect, as a general 
rule, to find it still in action; and this is the case if 
varieties be incipient species. Moreover, the species of 
the larger genera, which afford the greater number of 
varieties or incipient species, retain to a certain degree 
the character of varieties; for they differ from each 
other by a less amount of difference than do the species 
of smaller genera. The closely allied species also of the 
larger genera apparently have restricted ranges, and in 
their aflSnities they are clustered in little groups round 
other species—in which respects they resemble varieties. 
These are strange relations on the view of each species 
having been independently created, but are intelligible 
if all species first existed as varieties. 
As each species tends by its geometrical ratio of 
reproduction to increase inordinately in number ; and 
as the modified descendants of each species will be 
enabled to increase by so much the more as they 
become diversified in habits and structure, so as to be 
enabled to seize on many and widely difierent places 
in the economy of nature, there will be a constant 
tendency in natural seleption to preserve the most 
divergent offspring of any one species. Hence during a 
long-continued course of modification, the slight difler- 
ences, characteristic of varieties of the same species, 
tend to be augmented into the greater differences cha¬ 
racteristic of species of the same genus. New and im¬ 
proved varieties will inevitably supplant and exterminate 
the older, less improved and intermediate varieties; and 
thus species are rendered to a large extent defined and 
distinct objects. Dominant species belonging to the 
