112 
NATURAL SELECTION. 
Chap. IV. 
this head from our domestic productions. We shall here 
find something analogous. A fancier is struck by a 
pigeon having a slightly shorter beak ; another fancier 
is struck by a pigeon having a rather longer beak; and 
on the acknowledged principle that “ fanciers do not 
and will not admire a medium standard, but like ex¬ 
tremes,” they both go on (as has actually occurred 
with tumbler-pigeons) choosing and breeding from birds 
with longer and longer beaks, or with shorter and 
shorter beaks. Again, we may suppose that at an early 
period one man preferred swifter horses; another 
stronger and more bulky horses. The early differences 
would be very slight; in the course of time, from the 
continued selection of swifter horses by some breeders, 
and of stronger ones by others, the differences would 
become greater, and would be noted as forming two 
sub-breeds; finally, after the lapse of centuries, the sub¬ 
breeds would become converted into two well-established 
and distinct breeds. As the differences slowly become 
greater, the inferior animals with intermediate cha¬ 
racters, being neither very swift nor very strong, will 
have been neglected, and will have tended to disappear. 
Here, then, we see in man’s productions the action of 
what may be called the principle of divergence, causing 
differences, at first barely appreciable, steadily to in¬ 
crease, and the breeds to diverge in character both 
from each other and from their common parent. 
But how, it may be asked, can any analogous prin¬ 
ciple apply in nature ? I believe it can and does apply 
most efficiently, from the simple circumstance that the 
more diversified the descendants from any one species 
become in structure, constitution, and habits, by so much 
will they be better enabled to seize on many and widely 
diversified places in the polity of nature, and so be 
enabled to increase in numbers. 
