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The Perpetuation of Living Beings; hereditary transmission and variation by Thomas Henry Huxley
page 6 of 20 (30%)
always is, speaking broadly, to reproduce the form of the parents. The
proverb has it that the thistle does not bring forth grapes; so, among
ourselves, there is always a likeness, more or less marked and
distinct, between children and their parents. That is a matter of
familiar and ordinary observation. We notice the same thing occurring
in the cases of the domestic animals--dogs, for instance, and their
offspring. In all these cases of propagation and perpetuation, there
seems to be a tendency in the offspring to take the characters of the
parental organisms. To that tendency a special name is given-- it is
called 'Atavism', it expresses this tendency to revert to the ancestral
type, and comes from the Latin word 'atavus', ancestor.

Well, this 'Atavism' which I shall speak of, is, as I said before, one
of the most marked and striking tendencies of organic beings; but, side
by side with this hereditary tendency there is an equally distinct and
remarkable tendency to variation. The tendency to reproduce the
original stock has, as it were, its limits, and side by side with it
there is a tendency to vary in certain directions, as if there were two
opposing powers working upon the organic being, one tending to take it
in a straight line, and the other tending to make it diverge from that
straight line, first to one side and then to the other.

So that you see these two tendencies need not precisely contradict one
another, as the ultimate result may not always be very remote from what
would have been the case if the line had been quite straight.

This tendency to variation is less marked in that mode of propagation
which takes place asexually; it is in that mode that the minor
characters of animal and vegetable structures are most completely
preserved. Still, it will happen sometimes, that the gardener, when he
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