Lord Spencer
and others have shown how the cattle of England have increased in
weight and in early maturity, compared with the stock formerly kept in
this country. By comparing the accounts given in old pigeon treatises
of carriers and tumblers with these breeds as now existing in Britain,
India, and Persia, we can, I think, clearly trace the stages through
which they have insensibly passed, and come to differ so greatly from
the rock-pigeon.
Youatt gives an excellent illustration of the effects of a course of
selection, which may be considered as unconsciously followed, in so
far that the breeders could never have expected or even have wished to
have produced the result which ensued--namely, the production of two
distinct strains. The two flocks of Leicester sheep kept by Mr.
Buckley and Mr. Burgess, as Mr. Youatt remarks, "have been purely bred
from the original stock of Mr. Bakewell for upwards of fifty years.
There is not a suspicion existing in the mind of any one at all
acquainted with the subject that the owner of either of them has
deviated in any one instance from the pure blood of Mr. Bakewell's
flock, and yet the difference between the sheep possessed by these two
gentlemen is so great that they have the appearance of being quite
different varieties."
If there exist savages so barbarous as never to think of the inherited
character of the offspring of their domestic animals, yet any one
animal particularly useful to them, for any special purpose, would be
carefully preserved during famines and other accidents, to which
savages are so liable, and such choice animals would thus generally
leave more offspring than the inferior ones; so that in this case
there would be a kind of unconscious selection going on.
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