CIRGTTMSTANCES FAVORABLE TO SELECTION. 35 



the materials for selection to work on; not that mere in- 

 dividual 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 part of Yorkshire, ^'As they generally 

 belong to poor people, and are mostly iyi small lots, they 

 never can be improved. ^^ On the other hand, nurserymen, 

 from keeping large stocks of the same plant, are generally 

 far more successful than amateurs in raising new and 

 valuable varieties. A large number of individuals of an 

 animal or plant can be reared only v,diere the conditions for its 

 propagation are favorable. When the individuals are scanty 

 all will be allowed to breed, whatever their quality may be, 

 and this will effectually prevent selection. But probably the 

 most important element is that the animal or plant should 

 be so highly valued by man, that the closest attention is 

 paid to even the slightest deviations in its qualities or 

 structure. Unless such attention be paid nothing can be 

 effected. I have seen it gravely remarked, that it was 

 most fortunate that the strawberry began to vary just when 

 gardeners began to attend to this plant. Ko 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 (with some aid by crossing distinct species) 

 those many admirable varieties of the strawberry were 

 raised which have appeared during the last half-century. 



With animals, facility in preventing crosses is an im- 

 portant element in the formation of new races — at least, 

 in a country which is already stocked with other races. In 

 this respect inclosure of the land plays a part. Wander- 

 ing savages or the inhabitants of open plains rarely possess 

 more than one breed of the same species. Pigeons can be 

 mated for life, and this is a great convenience to the fancier, 

 for thus many races may be improved and kept true, 



