r Zoological
Gardens have become more productive since the year 1846. It is, also,
manifest from F. Cuvier's account of the Jardin des Plantes,[332] that the
animals formerly bred much less freely there than with us; for instance, in
the Duck tribe, which is highly prolific, only one species had at that
period produced young.

The most remarkable cases, however, are afforded by animals kept in
their native country, which, though perfectly tamed, quite healthy, and
allowed some freedom, are absolutely incapable of breeding.
Rengger,[333] who in Paraguay particularly attended to this subject,
specifies six quadrupeds in this condition; and he mentions two or
three others which most rarely {150} breed. Mr. Bates, in his admirable
work on the Amazons, strongly insists on similar cases;[334] and he
remarks, that the fact of thoroughly tamed native mammals and birds not
breeding when kept by the Indians, cannot be wholly accounted for by
their negligence or indifference, for the turkey is valued by them, and
the fowl has been adopted by the remotest tribes. In almost every part
of the world--for instance, in the interior of Africa, and in several
of the Polynesian islands--the natives are extremely fond of taming the
indigenous quadrupeds and birds; but they rarely or never succeed in
getting them to breed.

The most notorious case of an animal not breeding in captivity is that
of the elephant. Elephants are kept in large numbers in their native
Indian home, live to old age, and are vigorous enough for the severest
labour; yet, with one or two exceptions, they have never been known
even to couple, though both males and females have their proper
periodical seasons. If, however, we proceed a little eastward to Ava,
we hear from Mr. Crawfurd[335] that their "breeding in the domestic
state, or at least in the half-domestic state in which the female
elephants are generally kept, is of every-day occurrence;" and Mr.
Crawfurd informs me that he believes that the difference must be
attributed solely to the females being allowed to roam the forests with
some degree of freedom. The captive rhinoceros, on the other hand,
seems from Bishop Heber's account[336] to breed in India far more
readily than the elephant. Four wild species of the horse genus have
bred in Europe, though here exposed to a great change in their nat