ed from a continent at a very early period. The shallow sea
between the Peninsula of Malacca, Java, Sumatra and Borneo was probably
a continent or large island at an early epoch, and may have become
submerged as the volcanic ranges of Java and Sumatra were elevated. The
organic results we see in the very considerable number of species of
animals common to some or all of these countries, while at the same time
a number of closely allied representative species exist peculiar to
each, showing that a considerable period has elapsed since their
separation. The facts of geographical distribution and of geology may
thus mutually explain each other in doubtful cases, should the
principles here advocated be clearly established.

In all those cases in which an island has been separated from a
continent, or raised by volcanic or coralline action from the sea, or in
which a mountain-chain has been elevated in a recent geological epoch,
the phaenomena of peculiar groups or even of single representative
species will not exist. Our own island is an example of this, its
separation from the continent being geologically very recent, and we
have consequently scarcely a species which is peculiar to it; while the
Alpine range, one of the most recent mountain elevations, separates
faunas and floras which scarcely differ more than may be due to climate
and latitude alone.

The series of facts alluded to in Proposition (3), of closely allied
species in rich groups being found geographically near each other, is
most striking and important. Mr. Lovell Reeve has well exemplified it in
his able and interesting paper on the Distribution of the Bulimi. It is
also seen in the Humming-birds and Toucans, little groups of two or
three closely allied species being often found in the same or closely
adjoining districts, as we have had the good fortune of personally
verifying. Fishes give evidence of a similar kind: each great river has
its peculiar genera, and in more extensive genera its groups of closely
allied species. But it is the same throughout Nature; every class and
order of animals will contribute similar facts. Hitherto no attempt has
been made to explain these singular phenomena, or to show how they have
arisen. Why are the genera of Palms and of Orchids in almost every case
confined to one hemisphere? Why are the closely allied species of
brown-backed Trogons all found in the East, and the green-backed in the
West? Why are the Macaws and the