Conditions of Existence as Affecting the Perpetuation of Living Beings

pubOne.info present you this wonderfully illustrated edition. 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