Chap. IT.] DIVERGENCE OF CHARACTER. 135 



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 varieties become augmented 

 into the greater difference between species ? That this 

 does habitually happen, we must infer from most of the 

 innumerable species throughout nature presenting well- 

 marked differences; whereas varieties, the supposed 

 prototypes and parents of future well-marked species, 

 present slight and ill-defined 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 dif- 

 ference 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 acknow- 

 ledged principle that " fanciers do not and will not admire 

 a medium 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 



