climatai 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, hut 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 contradiction. Borneo and
New Guinea, as alike physically as two distinct countries
can be, are zoologically wide as the poles asunder ; while
Australia, with its dry winds, its open plains, its stony
deserts, and its temperate climate, yet produces birds and
quadrupeds which are closely related to those inhabiting
the hot damp luxuriant forests which everywhere clothe
the plains and mountains of New Guinea.
In order to illustrate more clearly the means by which
1 suppose this great contrast has been brought about, let
us consider what would occur if two strongly contrasted
divisions of the earth were, by natural means, brought
into proximity. No two parts of the World differ so
radically in their productions as Asia and Australia, but
the difference between Africa and South America is also
very great, and these two regions will well serve to illustrate
the question we are considering. On the one side
we have baboons, lions, elephants, buffaloes,^and giraffes;
on the other spider-monkeys, pumas, tapirs, ant-eaters,
and sloths; while among birds, the hornbills, turacos,
orioles, and honeysuckers of Africa contrast strongly with
the toucans, macaws, chatterers, and humming-birds of
America.
Now let us endeavour to imagine (what it is very
probable may occur in future ages) that a slow upheaval
of the bed of the Atlantic should take place, while at the
same time earthquake-shocks and volcanic action on the
land should cause increased volumes of sediment to be
poured down by the rivers, so that the two continents
should gradually spread out by the addition of newly-
formed lands, and thus reduce the Atlantic which now
separates them to an arm of the sea a few hundred miles