Origin of Species Variorum

become rarer and rarer, and finally extinct. The forms which stand in closest competition with those under-going modification and improvement, will naturally suffer most. And we have seen in the chapter on the Struggle for ... Existence that it is the most closely-allied forms,— varieties of the same species, and species of the same genus or of related genera,— which, from having nearly the same structure, constitution, and habits, generally come into the severest competition with each other. Consequently, each new variety or species, during the progress of its formation, will generally press hardest on its nearest kindred, and tend to exterminate them. We see the same process of extermination amongst our domesticated productions, through the selection of improved forms by man. Many curious instances could be given showing how quickly new breeds of cattle, sheep, and other animals, and varieties of flowers, take the place of older and inferior kinds. In Yorkshire, it is historically known that the ancient black cattle were displaced by the long-horns, and that these "were swept away by the short-horns" (I quote the words of an agricultural writer) "as if by some murderous pestilence."

Divergence of Character.

The principle, which I have designated by this term, is of high importance, ... and explains, as I believe, several important facts. In the first place, varieties, even strongly-marked ones, though having somewhat of the character of species— as is shown by the hopeless doubts in many cases how to rank them— yet certainly differ from each other far less than do good and distinct species. Nevertheless, according to my view, varieties are species in the process of formation, or are, as I have called them, incipient species. How, then, does the