We have even slight differences in the
horns of different breeds of cattle in relation to an artificially
imperfect state of the male sex; for oxen of certain breeds have
longer horns than in other breeds, in comparison with the horns of the
bulls or cows of these same breeds. Hence I can see no real difficulty
in any character having become correlated with the sterile condition
of certain members of insect-communities: the difficulty lies in
understanding how such correlated modifications of structure could
have been slowly accumulated by natural selection.
This difficulty, though appearing insuperable, is lessened, or, as I
believe, disappears, when it is remembered that selection may be
applied to the family, as well as to the individual, and may thus gain
the desired end. Thus, a well-flavoured vegetable is cooked, and the
individual is destroyed; but the horticulturist sows seeds of the same
stock, and confidently expects to get nearly the same variety;
breeders of cattle wish the flesh and fat to be well marbled together;
the animal has been slaughtered, but the breeder goes with confidence
to the same family. I have such faith in the powers of selection, that
I do not doubt that a breed of cattle, always yielding oxen with
extraordinarily long horns, could be slowly formed by carefully
watching which individual bulls and cows, when matched, produced oxen
with the longest horns; and yet no one ox could ever have propagated
its kind.
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