377] kept for more than eight years some wild
geese (_Anser Canadensis_), but they would not mate; whilst other
individuals of the same species produced young during the second year.
I know of but one instance in the whole family of a species which
absolutely refuses to breed in captivity, namely, the _Dendrocygna
viduata_, although, according to Sir R. Schomburgk,[378] it is easily
tamed, and is frequently kept by the Indians of Guiana. Lastly, with
respect to Gulls, though many have been kept in the Zoological Gardens
and in the old Surrey Gardens, no instance was known before the year
1848 of their coupling or breeding; but since that period the herring
gull (_Larus argentatus_) has bred many times in the Zoological Gardens
and at Knowsley.

There is reason to believe that insects are affected by confinement
like the higher animals. It is well known that the Sphingidae rarely
breed when thus treated. An entomologist[379] in Paris kept twenty-five
specimens of _Saturnia pyri_, but did not succeed in getting a single
fertile egg. A number of females of _Orthosia munda_ and of _Mamestra
suasa_ reared in confinement were unattractive to the males.[380] Mr.
Newport kept nearly a hundred individuals of two species of Vanessa,
but not one paired; this, however, might have been due to their habit
of coupling on the wing.[381] Mr. Atkinson could never succeed in India
in making the Tarroo silk-moth breed in confinement.[382] It appears
that a number of moths, especially the Sphingidae, when hatched in the
autumn out of their proper season, {158} are completely barren; but
this latter case is still involved in some obscurity.[383]

Independently of the fact of many animals under confinement not coupling,
or, if they couple, not producing young, there is evidence of another kind,
that their sexual functions are thus disturbed. For many cases have been
recorded of the loss by male birds when confined of their characteristic
plumage. Thus the common linnet (_Linota cannabina_) when caged does not
acquire the fine crimson colour on its breast, and one of the buntings
(_Emberiza passerina_) loses the black on its head. A Pyrrhula and an
Oriolus have been observed to assume the quiet plumage of the hen-bird; and
the _Falco albidus_ returned to the dress of an earlier age.[384] Mr.
Thomson, the superintendent of the Knowsley menagerie, info