the cat, the donkey, peacock, goose, &c.,
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 {43} 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, &c., 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 slowly, but more efficiently, is by far the
predominant Power.

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CHAPTER I