cross with a bull-dog has affected for many generations the courage and
obstinacy of greyhounds; and a cross with a greyhound has given to a
whole family of shepherd-dogs a tendency to hunt hares. These domestic
instincts, when thus tested by crossing, resemble natural instincts,
which in a like manner become curiously blended together, and for a
long period exhibit traces of the instincts of either parent: for
example, Le Roy describes a dog, whose great-grandfather was a wolf,
and this dog showed a trace of its wild parentage only in one way, by
not coming in a straight line to his master when called.
Domestic instincts are sometimes spoken of as actions which have become
inherited solely from long-continued and compulsory habit, but this, I
think, is not true. No one would ever have thought of teaching, or
probably could have taught, the tumbler-pigeon to tumble, an action
which, as I have witnessed, is performed by young birds, that have
never seen a pigeon tumble. We may believe that some one pigeon showed
a slight tendency to this strange habit, and that the long-continued
selection of the best individuals in successive generations made
tumblers what they now are; and near Glasgow there are house-tumblers,
as I hear from Mr. Brent, which cannot fly eighteen inches high without
going head over heels. It may be doubted whether any one would have
thought of training a dog to point, had not some one dog naturally
shown a tendency in this line; and this is known occasionally to
happen, as I once saw in a pure terrier. When the first tendency was
once displayed, methodical selection and the inherited effects of
compulsory training in each successive generation would soon complete
the work; and unconscious
selection is still at work, as each man tries to procure, without
intending to improve the breed, dogs which will stand and hunt best. On
the other hand, habit alone in some cases has sufficed; no animal is
more difficult to tame than the young of the wild rabbit; scarcely any
animal is tamer than the young of the tame rabbit; but I do not suppose
that domestic rabbits have ever been selected for tameness; and I
presume that we must attribute the whole of the inherited change from
extreme wildness to extreme tameness, simply to habit and
long-continued close confinement.
Natural instincts are lost under domestication: a remarkable instance
of this is seen in those breeds of fowls which very rarely or never
become broody, that is, never wish to sit on their eggs. Familiarity
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