The Project Gutenberg EBook of The Conditions Of Existence As Affecting
The Perpetuation Of Living Beings, by Thomas H. Huxley

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Title: The Conditions Of Existence As Affecting The Perpetuation Of Living Beings
Lecture V. (of V.), Lectures To Working Men, at the Museum
of Practical Geology, 1863, On Darwin's work: "Origin of
Species".

Author: Thomas H. Huxley

Posting Date: January 4, 2009 [EBook #2925]
Release Date: November, 2001

Language: English

Character set encoding: ASCII

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THE CONDITIONS OF EXISTENCE AS AFFECTING THE PERPETUATION OF LIVING
BEINGS

Lecture V. (of VI.), Lectures To Working Men, at the Museum of Practical
Geology, 1863, On Darwin's work: "Origin of Species".

By Thomas H. Huxley

IN the last Lecture I endeavoured to prove to you that, while, as a
general rule, organic beings tend to reproduce their kind, there is
in them, also, a constantly recurring tendency to vary--to vary to a
greater or to a less extent. Such a variety, I pointed out to you, might
arise from causes which we do not understand; we therefore called it
spontaneous; and it might come into existence as a definite and marked
thing, without any gradations between itself and the form which preceded
it. I further pointed out, that such a variety having once arisen,
might be perpetuated to some extent, and indeed to a very marked extent,
without any direct interference, or without any exercise of that process
which we called selection. And then I stated further, that by such
selection, when exercised artificially--if you took care to breed only
from those forms which presented the same peculiarities of any variety
which had arisen in this manner--the variation might be perpetuated, as
far as we can see, indefinitely.

The next question, and it is an important one for us, is this: Is there
any limit to the amount of variation from the primitive stock which can
be produced by this process of selective breeding? In considering this
question, it will be useful to class the characteristics, in respect of
which organic beings vary, under tw