a pouch or
gular sac, opening under the tongue. This extraordinary feature, first
discovered by James Douglas, a Scottish physician, and made known by
Eleazar Albin in 1740, though its existence was hinted by Sir Thomas Browne
sixty years before, if not by the emperor Frederick II, has been found
wanting in examples that, from the exhibition of all the outward marks of
virility, were believed to be thoroughly mature; and as to its function and
mode of development judgment had best be suspended, with the understanding
that the old supposition of its serving as a receptacle whence the bird
might supply itself or its companions with water in dry places must be
deemed to be wholly untenable. The structure of this pouch--the existence
of which in some examples has been well established--is, however, variable;
and though there is reason to believe that in one form or another it is
more or less common to several exotic species of the family _Otididae_, it
would seem to be as inconstant in its occurrence as in its capacity. As
might be expected, this remarkable feature has attracted a good deal of
attention (_Journ. fuer Ornith._, 1861, p. 153; _Ibis_, 1862, p. 107; 1865,
p. 143; _Proc. Zool. Soc._, 1865, p. 747; 1868, p. 741; 1869, p. 140; 1874,
p. 471), and the later researches of A.H. Garrod show that in an example of
the Australian bustard (_Otis australis_) examined by him there was,
instead of a pouch or sac, simply a highly dilated oesophagus--the
distension of which, at the bird's will, produced much the same appearance
and effect as that of the undoubted sac found at times in the _O. tarda_.

The distribution of the bustards is confined to the Old World--the bird so
called in the fur-countries of North America, and thus giving its name to a
lake, river and cape, being the Canada goose (_Bernicla canadensis_). In
the Palaearctic region we have the _O. tarda_ already mentioned, extending
from Spain to Mesopotamia at least, and from Scania to Morocco, as well as
a smaller species, _O. tetrax_, which often occurs as a straggler in, but
was never an inhabitant of, the British Islands. Two species, known
indifferently by the name of houbara (derived from the Arabic), frequent
the more southern portions of the region, and one of them, _O. macqueeni_,
though having the more eastern range and reaching India, has several times
occurred in north-western Europe, and once even in England. In the east of
Siberia the place of _O. tarda