imported dogs, would not breed though repeatedly crossed in the Jardin des
Plantes. (1/50. On authority of F. Cuvier quoted in Bronn's 'Geschichte der
Natur' b. 2 s. 164.) Some hounds from Central Africa, brought home by Major
Denham, never bred in the Town of London (1/51. W.C.L. Martin 'History of
the Dog' 1845 page 203. Mr. Philip P. King, after ample opportunities of
observation, informs me that the Dingo and European dogs often cross in
Australia.); and a similar tendency to sterility might be transmitted to
the hybrid offspring of a wild animal. Moreover, it appears that in M.
Flourens' experiments the hybrids were closely bred in and in for three or
four generations; and this circumstance would most certainly increase the
tendency to sterility. Several years ago I saw confined in the Zoological
Gardens of London a female hybrid from an English dog and jackal, which
even in this the first generation was so sterile that, as I was assured by
her keeper, she did not fully exhibit her proper periods; but this case was
certainly exceptional, as numerous instances have occurred of fertile
hybrids from these two animals. In almost all experiments on the crossing
of animals there are so many causes of doubt, that it is extremely
difficult to come to any positive conclusion. It would, however, appear,
that those who believe that our dogs are descended from several species
will have not only to admit that their offspring after a long course of
domestication generally lose all tendency to sterility when crossed
together; but that between certain breeds of dogs and some of their
supposed aboriginal parents a certain degree of sterility has been retained
or possibly even acquired.

Notwithstanding the difficulties in regard to fertility given in the last
two paragraphs, when we reflect on the inherent improbability of man having
domesticated throughout the world one single species alone of so widely
distributed, so easily tamed, and so useful a group as the Canidae; when we
reflect on the extreme antiquity of the different breeds; and especially