CHAPTER I. VARIATION UNDER DOMESTICATION.
7. CIRCUMSTANCES FAVOURABLE TO MAN'S POWER OF SELECTION.
I will now say a few words on the circumstances, favourable or the reverse,
to man's power of selection. A high degree of variability is obviously
favourable, as freely giving the materials for selection 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 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 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.