ponds of fresh water. Farmers find that they can raise most food by a
rotation of plants belonging to the most different orders; Nature follows
what may be called a simultaneous rotation. Most of the animals and plants
which live close round any small piece of ground could live on it (supposing
it not to be in any way peculiar in its nature), and may be said to be
striving to the utmost to live there; but it is seen that, where they come
into the closest competition with each other, the advantages of
diversification of structure, with the accompanying differences of habit
and constitution, determine that the inhabitants, which thus jostle each
other most closely, shall, as a general rule, belong to what we call
different genera and orders."--(p. 114.)


The abundance of some forms, the rarity and final extinction of many
others, and the consequent divergence of character or increase of
difference among the surviving representatives, are other consequences. As
favored forms increase, the less favored must diminish in number, for there
is not room for all; and the slightest advantage, at first probably
inappreciable to human observation, must decide which shall prevail and
which must perish, or be driven to another and for it more favorable
locality.

We cannot do justice to the interesting chapter upon natural selection by
separated extracts. The following must serve to show how the principle is
supposed to work:


"If during the long course of ages, and under varying conditions of life,
organic beings vary at all in the several parts of their organization, and
I think this cannot be disputed; if there be, owing to the high geometrical