of them may never have been actually joined to it. This continent must
have been broken up not only before the Western Islands were separated
from Asia, but probably before the extreme southeastern portion of Asia
was raised above the waters of the ocean; for a great part of the
land of Borneo and Java is known to be geologically of quite recent
formation, while the very great difference of species, and in many cases
of genera also, between the productions of the Eastern Malay Islands and
Australia, as well as the great depth of the sea now separating them,
all point to a comparatively long period of isolation.
It is interesting to observe among the islands themselves how a shallow
sea always intimates a recent land connexion. The Aru Islands, Mysol,
and Waigiou, as well as Jobie, agree with New Guinea in their species of
mammalia and birds much more closely than they do with the Moluccas,
and we find that they are all united to New Guinea by a shallow sea.
In fact, the 100-fathom line round New Guinea marks out accurately the
range of the true Paradise birds.
It is further to be noted--and this is a very interesting point in
connection with theories of the dependence of special forms of life
on external conditions--that this division of the Archipelago into
two regions characterised by a striking diversity in their natural
productions does not in any way correspond to the main physical or
climatal divisions of the surface. The great volcanic chain runs through
both parts, and appears to produce no effect in assimilating their
productions. Borneo closely resembles New Guinea not only in its vast
size and its freedom from volcanoes, but in its variety of geological
structure, its uniformity of climate, and the general aspect of the
forest vegetation that clothes its surface. The Moluccas are the
counterpart of the Philippines in their volcanic structure, their
extreme fertility, their luxuriant forests, and their frequent
earthquakes; and Bali with the east end of Java has a climate almost
as dry and a soil almost as arid as that of Timor. Yet between these
corresponding groups of islands, constructed as it were after the same
pattern, subjected to the same climate, and bathed by the same oceans,
there exists the greatest possible contrast when we compare their animal
productions. Nowhere does the ancient doctrine--that differences
or similarities in the various forms of life that inhabit different
countries are due to corresponding physical differences or similarities
in the countries themselves--meet with so direct and palpable a
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