Page:Evolution of Life (Henry Cadwalader Chapman, 1873).djvu/200

150 know that variations appear among wild animals, and that these variations are transmitted to their posterity. Is there then also a selection in nature which brings about the same results as that produced by man's selection? Suppose, for example, a number of plants are growing in a dry place, it is evident that those plants whose leaves are most thickly haired will be favored in the struggle for water, since the hairs are useful in taking up moisture. These plants will therefore survive and reproduce their kind, while those whose leaves are deficient in hairs will die out. But in the next generation some of the plants will be characterized by still thicker hairs; these will therefore be preserved and procreate; but in the course of generations plants are produced through this Natural Selection which differ very considerably from the parent stock, not only in the hairing of the leaves, but in other peculiarities, as one variation sooner or later entails another. Thus the moisture taken up by the hairs furnishes a large amount of nutriment, but if the nutriment is increased the flowering organs diminish; but this effect in the struggle for existence will bring about other variations, and so on indefinitely." The wingless condition of so many Madeira beetles is mainly due to the action of natural selection, but combined probably with disuse. For during many successive generations, each individual beetle which flew least, either from its wings having been ever so little less perfectly developed, or from indolent habit, will have had the best chance of surviving from not being blown out to sea; and, on the other hand, those beetles which most readily took to flight would oftenest have been blown to sea, and thus have been destroyed." Through the Survival of the Fittest, by Natural Selection, we see why animals resemble in color, etc. their surroundings or the places they live in. Thus, the Plant-lice and many insects are green, like the leaves they live upon. The Jumping Mouse, Fox, Lion, and Gazelle are yellow or yellowish-brown, like the