Chap. IV.] DIVERGENCE OF CHARACTER. 135 



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 dif- 

 ference between species? That this does habitually 

 happen, we must infer from most of the innumerable 

 species throughout nature presenting well-marked dif- 

 ferences; 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 dif- 

 fer 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 fan- 

 cier is, for instance, struck by a pigeon having a slightly 

 shorter beak; another fancier is struck by a pigeon hav- 

 ing a rather longer beak; and on the acknowledged 

 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 tum- 

 bler-pigeon) choosing and breeding from birds with 

 longer and longer beaks, or with shorter and shorter 

 beaks. Again, we may suppose that at ah early period of 

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