we do sometimes see are almost always imported from some other country,
often from islands. Although I do not doubt that some domestic animals
vary less than others, yet the rarity or absence of distinct breeds of
the cat, the donkey, peacock, goose, etc., may be attributed in main
part to selection not having been brought into play: in cats, from the
difficulty in pairing them; in donkeys, from only a few being kept by
poor people, and little attention paid to their breeding; in peacocks,
from not being very easily reared and a large stock not kept; in geese,
from being valuable only for two purposes, food and feathers, and more
especially from no pleasure having been felt in the display of distinct
breeds.
To sum up on the origin of our Domestic Races of animals and plants. I
believe that the conditions of life, from their action on the
reproductive system, are so far of the highest importance as causing
variability. I do not believe that variability is an inherent and
necessary contingency, under all circumstances, with all organic
beings, as some authors have thought. The effects of variability are
modified by various degrees of inheritance and of reversion.
Variability is governed by many unknown laws, more especially by that
of correlation of growth. Something may be attributed to the direct
action of the conditions of life. Something must be attributed to use
and disuse. The final result is thus rendered infinitely complex. In
some cases, I do not doubt that the intercrossing of species,
aboriginally distinct, has played an important part in the origin of
our domestic productions. When in any country several domestic breeds
have once been established, their occasional intercrossing, with the
aid of selection, has, no doubt, largely aided in the formation of new
sub-breeds; but the importance of the crossing of varieties has, I
believe, been greatly exaggerated, both in regard to animals and to
those plants which are propagated by seed. In plants which are
temporarily propagated by cuttings, buds, etc., the importance of the
crossing both of distinct species and of varieties is immense; for the
cultivator here quite disregards the extreme variability both of
hybrids and mongrels, and the frequent sterility of hybrids; but the
cases of plants not propagated by seed are of little importance to us,
for their endurance is only temporary. Over all these causes of Change
I am convinced that the accumulative action of Selection, whether
applied methodically and more quickly, or unconsciously and more
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