e researches, in regard to the great
Malay Archipelago, which is traversed near Celebes by a space of deep
ocean, and this separates two widely distinct mammalian faunas. On
either side, the islands stand on a moderately shallow submarine
bank, and these islands are inhabited by the same or by closely allied
quadrupeds. I have not as yet had time to follow up this subject in all
quarters of the world; but as far as I have gone, the relation holds
good. For instance, Britain is separated by a shallow channel from
Europe, and the mammals are the same on both sides; and so it is with
all the islands near the shores of Australia. The West Indian Islands,
on the other hand, stand on a deeply submerged bank, nearly one thousand
fathoms in depth, and here we find American forms, but the species and
even the genera are quite distinct. As the amount of modification which
animals of all kinds undergo partly depends on the lapse of time, and as
the islands which are separated from each other, or from the mainland,
by shallow channels, are more likely to have been continuously united
within a recent period than the islands separated by deeper channels, we
can understand how it is that a relation exists between the depth of the
sea separating two mammalian faunas, and the degree of their affinity,
a relation which is quite inexplicable on the theory of independent acts
of creation.
The foregoing statements in regard to the inhabitants of oceanic
islands, namely, the fewness of the species, with a large proportion
consisting of endemic forms--the members of certain groups, but not
those of other groups in the same class, having been modified--the
absence of certain whole orders, as of batrachians and of terrestrial
mammals, notwithstanding the presence of aerial bats, the singular
proportions of certain orders of plants, herbaceous forms having been
developed into trees, etc., seem to me to accord better with the belief
in the efficiency of occasional means of transport, carried on during
a long course of time, than with the belief in the former connection of
all oceanic islands with the nearest continent; for on this latter
view it is probable that the various classes would have immigrated more
uniformly, and from the species having entered in a body, their mutual
relations would not have been much disturbed, and consequently, they
would either have not been modified, or all the species in a more
equable manner.
I do not deny th
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