powers of increase of each species, at some age, season, or year, a severe
struggle for life, and this certainly cannot be disputed: then, considering
the infinite complexity of the relations of all organic beings to each
other and to their conditions of existence, causing an infinite diversity
in structure, constitution, and habits, to be advantageous to them, I think
it would be a most extraordinary fact if no variation ever had occurred
useful to each being's own welfare, in the same way as so many variations
have occurred useful to man. But if variations useful to any organic being
do occur, assuredly individuals thus characterized will have the best
chance of being preserved in the struggle for life; and from the strong
principle of inheritance they will tend to produce offspring similarly
characterized. This principle of preservation I have called, for the sake
of brevity, Natural Selection."--(pp. 126, 127.)


"In order to make it clear how, as I believe, natural selection acts, I
must beg permission to give one or two imaginary illustrations. Let us take
the case of a wolf, which preys on various animals, securing some by craft,
some by strength, and some by fleetness; and let us suppose that the
fleetest prey, a deer for instance, had from any change in the country
increased in numbers, or that other prey had decreased in numbers, during
that season of the year when the wolf is hardest pressed for food. I can
under such circumstances see no reason to doubt that the swiftest and
slimmest wolves would have the best chance of surviving, and so be
preserved or selected--provided always that they retained strength to
master their prey at this or at some other period of the year, when they
might be compelled to prey on other animals. I can see no more reason to
doubt this than that man can improve the fleetness of his greyhounds by
careful and methodical selection, or by that unconscious selection which
results from each man trying to keep the best dogs without any thought of