erent countries, strongly marked; and especially as the necessary
means of their transport are more evident, and confusion, from the
accidental conveyance by man of a species from one district to another
district, is less likely to arise. It is known that all mammifers (as
well as all other organisms) are united in one great system; but that
the different species, genera, or families of the same order inhabit
different quarters of the globe. If we divide the land{341} into two
divisions, according to the amount of difference, and disregarding the
numbers of the terrestrial mammifers inhabiting them, we shall have
first Australia including New Guinea; and secondly the rest of the
world: if we make a three-fold division, we shall have Australia, S.
America, and the rest of the world; I must observe that North America is
in some respects neutral land, from possessing some S. American forms,
but I believe it is more closely allied (as it certainly is in its
birds, plants and shells) with Europe. If our division had been
four-fold, we should have had Australia, S. America, Madagascar (though
inhabited by few mammifers) and the remaining land: if five-fold,
Africa, especially the southern eastern parts, would have to be
separated from the remainder of the world. These differences in the
mammiferous inhabitants of the several main divisions of the globe
cannot, it is well known, be explained by corresponding differences in
their conditions{342}; how similar are parts of tropical America and
Africa; and accordingly we find some _analogous_ resemblances,--thus
both have monkeys, both large feline animals, both large Lepidoptera,
and large dung-feeding beetles; both have palms and epiphytes; and yet
the essential difference between their productions is as great as
between those of the arid plains of the Cape of Good Hope and the
grass-covered savannahs of La Plata{343}. Consider the distribution of
the Marsupialia, which are eminently characteristic of Australia, and in
a lesser degree of S. America; when we reflect that animals of this
division, feeding both on animal and vegetable matter, frequent the dry
open or wooded plains and mountains of Australia, the humid impenetrable
forests of New Guinea and Brazil; the dry rocky mountains of Chile, and
the grassy plains of Banda Oriental, we must look to some other cause,
than the nature of the country, for their absence in Africa and other
quarters of the world.

{341} This di