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 c...