Chap. I. CIRCUMSTANCES FAVOURABLE TO SELECTION. 41 



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 ap- 

 pearance 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 belong to poor 

 people, and are mostly in small lots, they never can be 

 improved." On the other hand, nurserymen, from raising 

 large stocks of the same plants, are generally far more 

 successful than amateurs in getting new and valuable 

 varieties. The keeping of a large number of individuals 

 of a species in any country requires that the species 

 should be placed under favourable conditions of life, so 

 as to breed freely in that country. When the individuals 

 of any species are scanty, all the individuals, whatever 

 their quality may be, will generally be allowed to breed, 

 and this will effectually prevent selection. But probably 

 the most important point of all, is, that the animal or 

 plant should be so highly useful to man, or so much 

 valued by him, that the closest attention should be 

 paid to even the slightest deviation in the qualities or 

 structure of each individual. Unless such attention 

 be paid nothing can be effected. I have seen it gravely 

 remarked, that it was most fortunate that the straw- 

 berry began to vary just when gardeners began to attend 

 closely to this plant. No doubt the strawberry had 

 always varied since it was cultivated, but the slight 

 varieties had been neglected. As soon, however, as 

 gardeners picked out individual plants with slightly 

 larger, earlier, or better fruit, and raised seedlings from 

 them, and again picked out the best seedlings and 

 bred from them, then, there appeared (aided by some 



