tory of any of
our domestic breeds. But, in fact, a breed, like a dialect of a language,
can hardly be said to have had a definite origin. A man preserves and
breeds from an individual with some slight deviation of structure, or takes
more care than usual in matching his best animals and thus improves them,
and the improved individuals slowly spread in the immediate neighbourhood.
But as yet they will hardly have a distinct name, and from being only
slightly valued, their history will be disregarded. When further improved
by the same slow and gradual process, they will spread more widely, and
will get recognised as something distinct and valuable, and will then
probably first receive a provincial name. In semi-civilised countries, with
little free communication, the spreading and knowledge of any new sub-breed
will be a slow process. As soon as the points of value of the new sub-breed
are once fully 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 civilization 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.

I must 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 {41} 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; and hence this comes to be of the highest importance to success. On
this principle Marshall has remarked, with respect to the sheep of parts of
Yorkshire, that "as they generally belong to poor people, and are mostly
_in small lots_, they never can be improved." On the other hand,
nurserymen, from raising large stocks of the same plants, are generally far
more successful than amateurs in getting new and valuable varieties. The
keeping of a large number of individuals of a speci