VARIATION UNDER DOMESTICATION 37 



breeds. But, in fact, a breed, like a dialect of a 

 language, can hardly be said to have had a definite 

 origin. A man preserves and breeds from an individual 

 with some slight deviation of structure, or takes more 

 care than usual in matching his best animals and thus 

 improves them, and the improved individuals slowly 

 spread in the immediate neighbourhood. But as yet 

 they will hardly have a distinct name, and from being 

 only slightly valued, their history will be disregarded. 

 When further improved by the same slow and gradual 

 process, they will spread more widely, and will get 

 recognised as something distinct and valuable, and will 

 then probably first receive a provincial name. In semi- 

 civilised countries, with little free communication, the 

 spreading and knowledge of any new sub-breed will b6 

 a slow process. As soon as the points of value of the 

 new sub-breed are once fully acknowledged, the prin- 

 ciple, as I have called it, of unconscious selection will 

 always tend, — perhaps more at one period than at 

 another, as the breed rises or falls in fashion, — perhaps 

 more in one district than in another, according to the 

 state of civilisation of the inhabitants — slowly to add 

 to the characteristic features of the breed, whatever 

 they may be. But the chance will be infinitely small 

 of any record having been preserved of such slow, 

 varying, and insensible changes. 



I must now say a few words on the circumstances, 

 favourable or the reverse, to man's power of selection. 

 A high degree of variability is obviously favourable, as 

 freely giving the materials for selection to work on ; 

 not that mere individual differences are not amply 

 sufficient, with extreme care, to allow of the accumula- 

 tion of a large amount of modification in almost any 

 desired direction. But as variations manifestly useful 

 or pleasing to man appear only occasionally, the chance 

 of their appearance will be much increased by a large 

 number of individuals being kept ; and hence this 

 comes to be of the highest importance to success. On 

 this principle Marshall has remarked, with respect to 

 the sheep of parts of Yorkshire, that ' as they generally 



