It will convince us of our ignorance on
the mutual relations of all organic beings; a conviction as necessary,
as it seems to be difficult to acquire. All that we can do, is to keep
steadily in mind that each organic being is striving to increase at a
geometrical ratio; that each at some period of its life, during some
season of the year, during each generation or at intervals, has to
struggle for life, and to suffer great destruction. When we reflect on
this struggle, we may console ourselves with the full belief, that the
war of nature is not incessant, that no fear is felt, that death is
generally prompt, and that the vigorous, the healthy, and the happy
survive and multiply.
CHAPTER 4.
NATURAL SELECTION.
Natural Selection: its power compared with man's selection, its power
on characters of trifling importance, its power at all ages and on
both sexes.
Sexual Selection.
On the generality of intercrosses between individuals of the same
species.
Circumstances favourable and unfavourable to Natural Selection,
namely, intercrossing, isolation, number of individuals.
Slow action.
Extinction caused by Natural Selection.
Divergence of Character, related to the diversity of inhabitants of
any small area, and to naturalisation.
Action of Natural Selection, through Divergence of Character and
Extinction, on the descendants from a common parent.
Explains the Grouping of all organic beings.
How will the struggle for existence, discussed too briefly in the last
chapter, act in regard to variation? Can the principle of selection,
which we have seen is so potent in the hands of man, apply in nature?
I think we shall see that it can act most effectually.
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