How strongly these domestic instincts, habits, and dispositions are
inherited, and how curiously they become mingled, is well shown when
different breeds of dogs are crossed. Thus it is known that a 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 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.
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