Now, as I am credited by all my scientific friends with having discovered the theory of natural selection more than fifty years ago, and as the whole reading public have had this hammered into them with needless repetition during the whole of that period, it is rather amusing to be told now that I do not know what natural selection is, nor what it implies. It is also a striking proof that the whole subject is now held to be so old and commonplace as not to be worth studying by a popular teacher before writing about it so strongly and dogmatically. If he had done so he would not deliberately assert that I hold opinions in regard to the matter which in several of my books I have shown the fallacy of. I propose, therefore, to give here a short account of the essential features of the theory of natural selection; how it has operated in bringing about the evolution of the almost infinitely varied forms of plants and of the lower animals; and also to explain as clearly as I can why, and to what extent, it has acted differently in the case of man. _Lamarckism and Darwinism—How they Differ_ The first great naturalist who put forward a detailed explanation of how he supposed the varied forms of animal life to have been produced was Lamarck, a contemporary of Buffon and Goethe, both of whom believed in evolution but offered no explanation of how it could have been brought about. Lamarck, however, suggested that the various organs of animals were modified by voluntary effort producing increased development, as when an antelope escapes from a lion by its swiftness, which swiftness is increased by the straining of its limbs in flight; while the long neck and fore-limbs of the giraffe were explained by the continual stretching of these parts of the body to obtain foliage for food during severe droughts. In addition to this other causes are at work, as described in the following passage, translated or paraphrased by Sir Charles Lyell in his _Principles of Geology_: "Every considerable alteration in the local conditions under which each race of animals exists causes a change in their wants, and these new wants excite them to new actions and habits. These actions require the more frequent employment of some parts before but slightly exercised, and then greater development follows as a consequence of their more frequent use. Other organs, no longer in use, are impoverished and diminished in size; nay, are sometimes entirely annihilated, while in their place new parts are insensibly produced for the discharge of new functions." Again, he says: