Origin of Species Variorum

number of generations, would be opposed to all experience. I may add, that, when under nature the conditions of life do change, variations and reversions of character probably do occur; but natural selection, as will hereafter be explained, will determine how far the new characters thus arising shall be preserved.

Character of Domestic Varieties; difficulty of distinguishing between Varieties and Species; origin of Domestic Varieties from one or more Species.

When we look to the hereditary varieties or races of our domestic animals and plants, and compare them with .. closely allied species, we generally perceive in each domestic race, as already remarked, less uniformity of character than in true species. Domestic races often ... have a somewhat monstrous character; by which I mean, that, although differing from each other, and from .. other species of the same genus, in several trifling respects, they often differ in an extreme degree in some one part, both when compared one with another, and more especially when compared with .. the species under nature to which they are nearest allied. With these exceptions (and with that of the perfect fertility of varieties when crossed, — a subject hereafter to be discussed), domestic races of the same species differ from each other, only in most cases in a lesser degree, in the same manner as do closely-allied species of the same genus in a state of nature. I think that this must be admitted, when we find that there are hardly any domestic races, either amongst animals or plants, which have not been ranked by .. competent judges as the descendants of aboriginally distinct species, and by other competent judges as mere varieties. If any marked distinction existed between domestic races and species, this source of doubt could not so perpetually recur. It