VARIATION UNDER DOMESTICATION 29 



which is now set on them, after several breeds have fairly been 

 established. It is known that with pigeons many slight variations 

 now occasionally appear, but these are rejected as faults or devia- 

 tions from the standard of perfection in each breed. The common 

 goose has not given rise to any marked varieties; hence the Tou- 

 louse and the common breed, which differ only in color, that most 

 fleeting of characters, have lately been exhibited as distinct at our 

 poultry shows. 



These views appear to explain what has sometimes been noticed, 

 namely, that we know hardly anything about the origin or history 

 of any of our domestic breeds. But, in fact, a breed, like a dialect 

 of a language, can hardly be said to have a distinct origin. A man 

 preserves and breeds from an individual with some slight devia- 

 tion of structure, or takes more care than usual in matching his 

 best animals, and thus improves them, and the improved animals 

 slowly spread in the immediate neighborhood. But they will as yet 

 hardly have a distinct name, and from being only slightly valued, 

 their history will have been disregarded. When further improved 

 by the same slow and gradual process, they will spread more 

 widely, and will be recognized as something distinct and valuable, 

 and will then probably first receive a provincial name. In semi- 

 civilized countries, with little free communication, the spreading 

 of a new sub-breed would be a slow process. As soon as the points 

 of value are once acknowledged, the principle, 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 civilization of the inhabitants — slowly to add to the character- 

 istic 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. 



CIRCUMSTANCES FAVORABLE TO MAN'S POWER OF SELECTION 



I will now say a few words on the circumstances, favorable or-^ 

 the reverse, to man's power of selection. A high degree of varia- 

 bility is obviously favorable, 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 accumulation 

 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. Hence, number is of 

 the highest importance for success. On this principle Marshall for- 



r 



