ad been previously known,--and as the mammals of islands, as
has been well remarked by Cuvier, are usually small, of this appreciable
proportion the bulk is comparatively not great. The great kangaroo
(_Macropus giganteus_), though the inhabitant of an island which ranks
among the continents, would not much exceed in bulk, tried by Raleigh's
quaint scale of measurement, a sheep and a half, or at most two sheep;
and yet I know not that discovery in the islands has added a larger
animal to the previously known ones than the great kangaroo. Mr.
Waterhouse, when he published, in 1841, his "History of the
Marsupialia," reckoned up one hundred and five distinct species of
pouched animals; and eighteen species more,--in all one hundred and
twenty-three,--have been since added to the order. With the exception of
an opossum or two, all these marsupiata may be regarded as discoveries
made since the time of Buffon; most of them, as I have said, are small.
And such, generally, has been the nature of the revelations made during
the last seventy years by positive _discovery_. It is not, however, by
discovery, but by scientific scrutiny into the true nature and
distinctions of species, that the recent enormous increase in the number
of the known mammals has mainly taken place. And in these cases it will
generally be found that the new species, which had been previously
confounded with some old ones, so nearly resemble the latter in bulk, as
well as aspect, as to justify in some degree the mistake. Let us take
two of the greatest animals as examples,--the elephant and the
rhinoceros. Buffon confounded the African with the Asiatic elephant. We
now know that they represent two well marked species, _Elephas
Africanus_ and _Elephas Indicus_; and that an ark which contained the
ancestors of all the existing animals would require to have its _two_
pair of elephants, not the one pair only which would have been deemed
sufficient eighty years ago. Again, with respect to the rhinoceros,
Buffon was acquainted with the single horned animal, and had _heard_ of
the animal with two horns; and so, though by no means certain that the
"_variety_ was constant," he yet held that "two distinct species might
possibly be established." But we now know that there are six species of
rhinoceros (seven, according to the "Physical Atlas,")--_Rh. Indicus_,
_Rh. Javanus_, _Rh. Sumatrensis_, _Rh. Africanus_, _Rh. simus_, and _Rh.
ketloa_; and that, instead of _possibly