by the force of inheritance to their offspring, will constitute new races, or what Mr. Darwin calls 'incipient species.' If one variety, being in other respects just equal to its competitors, happens to be more prolific, some of its offspring will stand a greater chance of being among those which will escape destruction, and their descendants, being in like manner very fertile, will continue to multiply at the expense of all less prolific varieties.
As breeders of domestic animals, when they choose certain varieties in preference to others to breed from, speak technically of their method as that of 'selecting,' Mr. Darwin calls the combination of natural causes, which may enable certain varieties of wild animals or plants to prevail over others of the same species, 'natural selection.'
A breeder finds that a new race of cattle with short horns or without horns may be formed, in the course of several generations, by choosing varieties having the most stunted horns as his stock from which to breed; so nature, by altering, in the course of ages, the conditions of life, the geographical features of a country, its climate, the associated plants and animals, and, consequently, the food and enemies of a species and its mode of life, may be said, by this means, to select certain varieties best adapted for the new state of things. Such new races may often supplant the original type from which they have diverged, although that type may have been perpetuated without modification for countless anterior ages in the same region, so long as it was in harmony with the surrounding conditions then prevailing.
Lamarck, when speculating on the origin of the long neck of the giraffe, imagined that quadruped to have stretched himself up in order to reach the boughs of lofty trees, until by continued efforts, and longing to reach higher, he obtained an elongated neck. Mr. Darwin and Mr. Wallace simply suppose that, in a season of scarcity, a longer-necked variety,
