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Show • 44: DARWINIAN A. upon natural selection by separated extracts. The following _must serve to show how the principle is supposed to work : "If during the long course of ages, and under varying conditions of life, organic beings vary at all in the several parts of their organization, and l think this cannot be disputed; if there be, owing to the high geometrical powers of increase of each species, at some age, seas~n, or year, a severe struggle for life, and this certainly cannot be disputed: then, considering the infinite complexity of the relations of all organic beings to each other and to their conditions of existence, causing an infinite diversity in structure, constitution, and habits, to be advantageous to them, I think it would be a most extraordinary fact if no variation ever had occurred useful to each being's own welfare, in the same way as so many variations have occurred useful to man. But if variations useful to any organic being do occur, assuredly individuals thus charactel'ized will have the best chance of being preserved in the struggle for life ; and from the strong principle of inheritance they will tend to produce offspring similarly characterized. This principle of preservation I have called, for the sake of brevity, Nat ural Selection."-(pp. 126, 127.) "In order to make it clear how, as I believe, natural !lelection acts, I must beg permission to give one or two imaginary illustPations. Let us take the case of a wolf, which preys on various animals, securing some by craft, some by strength, and some by fleetness; and let us suppose that the fleetest prey, a deer for instance, had from any change in the country increased in numbers, or that other prey had decreased in numbers, during that season of the year when the wolf is hardest pressed for food. I can under such circumstances see no reason to doubt that the swifte~t and slim~est wolves would have the best chance of surviving, and so be preserved or selected-provided always that they retained strength to master their prey at this or at some other period of the year, when they might be compelled to prey on other animals. I can see no more reason to doubt this than that man can improve the fleetness of his THE ORIGIN OF SPECIES. 45 greyhounds by careful and methodical selection, or by that unconscious select~on which results from each man trying to keep the best dogs w1thout any thought of modifying the breed. "Even without any change in the proportional numbers of the animals on which our wolf preyed, a cub might be born with an innate tendency to pursue certain kinds of prey. Nor can this be thought very improbable; for we often observe great differences in the natural tendencies of our domestic animals: one cat, for instance, taking to catchin(J' rats another • 0 , miCe; one cat, according to Mr. St. John, bringing home winged game, another hares or rabbits, and another hunting on marshy ground, and almost nightly catching woodcocks or snipes. The tendency to catch rats rather than mice is known to be inherited. Now, if any slight innate change of habit or of structure benefited an individual wolf, it would have the best chance of surviving and of leaving offspring. Some of its young would p.r?bably in~erit the same habits or structure, and by the repetitwn of thts process a new variety might bo formed which would either supplant or coexist with the parent-form of wolf. Or, again, the wolves inhabiting a mountainous district, and those _frequenting the lowlands, would naturally be forced to hunt different prey; and from a continued preservation of the individ~ als. best fitted for the two sites, two varieties might slowly be formed. These varieties wonld cross and blend where they met; but to thjs subject of intercrossing we shall soon have to rett~r~. I may add that, according to Mr. Pierce, there are two vanetles of the wolf inhabiting the Catskill Mountains in tl10 United States, one with a light greyhound-like form, which pursues deer, and the other more bulky, with shorter legs, which more frequently attacks the shepherd's flock."-(pp. 90, 91.) We eke out the illustration here with a counterpart instance, viz., the remark of Dr. Bachman that "the ~eer that reside pennanently in the SWai?pS o£ Oarolma are taller and longer-legged than those in the . higher grounds." 1 1 " Quadrupeds of America," vol. ti., p. 239. 3 |