a new sub-breed will be a slow process. As soon as the
points of value are once acknowledged, the principle, as I have called
it, of unconscious selection will always tend--perhaps more at one
period than at another, as the breed rises or falls in fashion--perhaps
more in one district than in another, according to the state of
civilisation of the inhabitants--slowly to add to the characteristic
features of the breed, whatever they may be. But the chance will be
infinitely small of any record having been preserved of such slow,
varying, and insensible changes.

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 slightl