In semi-civilised countries, with little free communication, the spreading of 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.