Chap. T.j CIRCUMSTANCES FAVOURABLE TO SELECTION. 29 



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 deviation 

 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 neighbourhood. But they will as yet 

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

 their history will ha^e been disregarded. When further improved 

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

 and will be 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 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 un- 

 conscious 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. 



to Man's Power of Selection. 

 I will now say a few words on the circumstances, favourable, or 

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

 ability 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 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 formerly remarked, with respect to the sheep of parts of 

 Yorkshire, " as they generally belong to poor people, and are mostly 

 in small lots, they never can be improved." On the other hand, 

 nurserymen, from keeping large stocks of the same plant, are gener- 

 ally far more successful than amateurs in raising new and valuable 

 varieties. A large number of individuals of an animal or plant caD 



