Just so with the types of organic life. It was not merely an
idle sneer of the witty Frenchman, that science has not yet explained
how an ancestor can transmit what he has not got himself. He cannot
always transmit all that he himself actually possesses of nature's
gifts. Vitality becomes lowered, and the type degenerates. Weismann has
emphasized this idea in his doctrine of "panmixia," or the withdrawal of
selection, which always results in degeneration. Selection, artificial
or natural, may serve to counteract this universal tendency of organic
life, but only approximately. As Sir William Dawson says, "All things
left to themselves tend to degenerate." Little by little the endowment
of vitality bestowed upon our world at the beginning has, like radiant
energy, been returned to God who gave it; but, unlike the case of
radiant energy, the Creator has not established any regular source of
vital supply from without, no elixir of life for organic nature in
general. There is no longer within easy reach a tree of life from which
we may pluck and eat and live forever. And as the individual grows old
and dies, so do species and even whole tribes degenerate and become
extinct.
"From scarped cliff and quarried stone
She cries, 'A thousand types are gone.
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