But At The Time When This Narrowing Of The Sea Took Place In One
Direction, There Must Have Been A Greater Separation At The Other End
Of The Chain, Or We Should Find More Equality In The Numbers Of
Identical And Representative Species Derived From Each Extremity.
It
is true that the widening of the strait at the Australian end by
subsidence, would, by putting a
Stop to immigration and intercrossing
of individuals from the mother country, have allowed full scope to the
causes which have led to the modification of the species; while the
continued stream of immigrants from Java, would, by continual
intercrossing, check such modification. This view will not, however,
explain all the facts; for the character of the fauna of the Timorese
group is indicated as well by the forms which are absent from it as by
those which it contains, and is by this kind of evidence shown to be
much more Australian than Indian. No less than twenty-nine genera, all
more or less abundant in Java, and most of which range over a wide
area, are altogether absent; while of the equally diffused Australian
genera only about fourteen are wanting. This would clearly indicate
that there has been, until recently, a wide separation from Java; and
the fact that the islands of Bali and Lombock are small, and are
almost wholly volcanic, and contain a smaller number of modified forms
than the other islands, would point them out as of comparatively
recent origin. A wide arm of the sea probably occupied their place at
the time when Timor was in the closest proximity to Australia; and as
the subterranean fires were slowly piling up the now fertile islands
of Bali and Lombock, the northern shores of Australia would be sinking
beneath the ocean. Some such changes as have been here indicated,
enable us to understand how it happens, that though the birds of this
group are on the whole almost as much Indian as Australian, yet the
species which are peculiar to the group are mostly Australian in
character; and also why such a large number of common Indian forms
which extend through Java to Bali, should not have transmitted a
single representative to the island further east.
The Mammalia of Timor as well as those of the other islands of the
group are exceedingly scanty, with the exception of bats. These last
are tolerably abundant, and no doubt many more remain to be discovered.
Out of fifteen species known from Timor, nine are found also in Java,
or the islands west of it; three are Moluccan species, most of which
are also found in Australia, and the rest are peculiar to Timor.
The land mammals are only seven in number, as follows: 1. The common
monkey, Macacus cynomolgus, which is found in all the Indo-Malayan
islands, and has spread from Java through Bali and Lombock to Timor.
This species is very frequent on the banks of rivers, and may have
been conveyed from island to island on trees carried down by hoods.
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