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. 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.
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