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    Conditions of Existence as Affecting the Perpetuation of Living Beings
    Conditions of Existence as Affecting the Perpetuation of Living Beings
    Conditions of Existence as Affecting the Perpetuation of Living Beings
    Ebook46 pages36 minutes

    Conditions of Existence as Affecting the Perpetuation of Living Beings

    By Thomas Henry Huxley

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    LanguageEnglish
    PublisherArchive Classics
    Release dateNov 15, 2013
    Conditions of Existence as Affecting the Perpetuation of Living Beings

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      Book preview

      Conditions of Existence as Affecting the Perpetuation of Living Beings - Thomas Henry Huxley

      The Project Gutenberg EBook of The Conditions Of Existence As Affecting

      The Perpetuation Of Living Beings, by Thomas H. Huxley

      This eBook is for the use of anyone anywhere at no cost and with

      almost no restrictions whatsoever.  You may copy it, give it away or

      re-use it under the terms of the Project Gutenberg License included

      with this eBook or online at www.gutenberg.org

      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

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

      Last Updated: January 22, 2013

      Language: English

      *** START OF THIS PROJECT GUTENBERG EBOOK THE CONDITIONS OF EXISTENCE ***

      Produced by Amy E. Zelmer, and David Widger

      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 two heads: we may consider structural characteristics, and we may consider physiological characteristics.

      In the first place, as regards structural characteristics, I endeavoured to show you, by the skeletons which I had upon the table, and by reference to a great many well-ascertained facts, that the different breeds of Pigeons, the Carriers, Pouters, and Tumblers, might vary in any of their internal and important structural characters to a very great degree; not only might there be changes in the proportions of the skull, and the characters of the feet and beaks, and so on; but that there might be an absolute difference in the number of the vertebrae of the back, as in the sacral vertebrae of the Pouter; and so great

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