Chap. I. CIRCUMSTANCES FAYOURABLE 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 
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 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 
