Seite - 122 - in The Origin of Species

122 ORIGIN OF SPECIES DIVERGENCE OF CHARACTER The principle, which I have designated by this term, is of high importance, and explains, as I believe, several impor- tant 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 far less from each other 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 lesser difference between varietiesbecome augmented into the greater difference between species? That this does habit- ually happen, we must infer from most of the innumerable species throughout nature presenting well-marked differ- ences ; whereas varieties, the supposed prototypes and par- ents of future well-marked species, present slight and ill-de- fined differences. Mere chance, as we may call it, might cause one variety to differ in some character from its parents, and the offspring of this variety again to differ from its parent in the very same character and in a greater degree; but this alone would never account for so habitual and large a degree of difference as that between the species of the same genus. As has always been my practice, I have sought light on this head from our domestic productions. We shall here find something analogous. It will be admitted that the production of races so different as short-horn and Hereford cattle, race and cart horses, the several breeds of pigeons, &c., could never have been effected by the mere chance accumulation of similar variations during many successive generations. In practice, a fancier is, for instance, struck by a pigeon having a slightly shorter beak ; another fancier is struck by a pigeon having a rather longer beak; and on the acknowledged principle that "fanciers do not and will not admire a me- dium standard, but like extremes," they both go on (as has actually occurred with the sub-breeds of the tumbler- pigeon) choosing and breeding from birds with longer and longer beaks, or with shorter and shorter beaks. Again, we may suppose that at an early period of history, the men of