On the other hand, cats, from their nocturnal
rambling habits, cannot be matched, and, although so much valued by
women and children, we hardly ever see a distinct breed kept up; such
breeds as 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.
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