But, in the second place, observation shows that
slight variations ARE perpetually being introduced with every
successive generation, and many of these variations are transmitted to
the generations that follow. In the course of time, therefore, from any
one parent stock would descend a very large variety of kinds. But if, in
the third place, it be asked why this variety does not range by
imperceptible degrees from extreme forms in one direction to extreme
forms in the other, the answer is to be found in the enormous
prodigality and the equally enormous waste of life and living creatures.
Plants and animals produce far more descendants than ever come even to
such maturity as to reproduce their kind. And this is particularly the
case with the lower forms of life. Eggs and seeds and germs are
destroyed by millions, and so in a less but still enormous proportion
are the young that come from those that have not been destroyed. There
is no waste like the waste of life that is to be seen in nature. Living
creatures are destroyed by lack of fit nourishment, by lack of means of
reproduction, by accidents, by enemies. The inevitable operation of this
waste, as Darwin's investigation showed, has been to destroy all those
varieties which were not well fitted to their surroundings, and to keep
those that were.
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