128 
KATUEAL SELECTIOK. 
Chap. IV. 
has acted in the world’s history, geology plainly de¬ 
clares. Natural selection, also, leads to divergence of 
character; for more living beings can be supported on 
the same area the more they diverge in structure, habits, 
and constitution, of which we see proof by looking to 
the inhabitants of any small spot or to naturalised pro¬ 
ductions. Therefore during the modification of the 
descendants of any one species, and during the incessant 
struggle of al] species to increase in numbers, the more 
diversified these descendants become, the better will be 
their chance of succeeding in the battle for life. Thus 
the small differences distinguishing varieties of the same 
species, steadily tend to increase till they come to equal 
the greater differences between species of the same 
genus, or even of distinct genera. 
We have seen that it is the common, the widely- 
diffused, and widely-ranging species, belonging to the 
larger genera, which vary most; and these tend to 
transmit to their modified offspring that superiority 
which now makes them dominant in their own coun¬ 
tries. Natural selection, as has just been remarked, 
leads to divergence of character and to much extinction 
of the less improved and intermediate forms of life. On 
these principles, I believe, the nature of the affinities 
of all organic beings may be explained. It is a truly 
wonderful fact—the wonder of which we are apt ta 
overlook from familiarity—that all animals and all 
plants throughout all time and space should be related 
to each other in group subordinate to group, in the 
manner which we everywhere behold—namely, vari¬ 
eties of the same species most closely related together, 
species of the same genus less closely and unequally 
related together, forming sections and sub-genera, spe¬ 
cies of distinct genera much less closely related, and 
genera related in different degrees, forming sub-fami- 
