CIRCUMSTANCES FAVORABLE TO SELECTION. 33 



CIRCUMSTANCES FAVORABLE TO MAN'S POWER OP 



SELECTION. 



I will now say a few words on the circumstances, favor- 

 able or the reverse, to man's power of selection. A high 

 degree of variability is obviously favorable, as freely giving 

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

 vidual 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 vari- 

 ations 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 in 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 val- 

 uable varieties. A large number of individuals of an ani- 

 mal or plant can be reared only where 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 qual- 

 ities 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. No doubt the 

 strawberry had always varied since it was cultivated, but 

 the slight variations 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 impor- 

 tant element in the formation of new races — at least, in a 

 country which is already stocked with other races. In this 



