each breed. The common goose has not given rise to any marked
varieties; hence the Thoulouse and the common breed, which differ only
in colour, that
most fleeting of characters, have lately been exhibited as distinct at
our poultry-shows.
I think these views further explain what has sometimes been
noticed namely that we know nothing about the origin or history 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 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.
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
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
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