28 CIRCUMSTANCES FAVOURABLE TO SELECTION. [CHAP. I. 



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 occa- 

 sionally, 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 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 where the conditions for its propagation are favourable. 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 

 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 (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 important 

 element in the formation of new races, at least, in a country which 

 is already stocked with other races. In this respect enclosure of the 

 land plays a part. Wandering 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, though 

 mingled in the same aviary; and this circumstance must have 

 largely favoured the formation of new breeds. Pigeons, I may add, 

 can be propagated in great numbers and at a very quick rate, and 

 inferior birds may be freely rejected, as when killed they serve for 

 food. On the other hand, cats, from their nocturnal rambling habits, 

 cannot be easily matched, and, although so much valued by women 

 and children, we rarely see a distinct breed long kept up ; such breeds 

 as we do sometimes see are almost always imported from some other 

 country. Although I do not doubt that some domestic animals 



