usual mode of growth to that of the Babirusa. In other respects there
seems no affinity between these animals, and the Babirusa stands
completely isolated, having no resemblance to the pigs of any other part
of the world. It is found all over Celebes and in the Sula islands,
and also in Bourn, the only spot beyond the Celebes group to which it
extends; and which island also shows some affinity to the Sula islands
in its birds, indicating perhaps, a closer connection between them at
some former period than now exists.
The other terrestrial mammals of Celebes are five species of squirrels,
which are all distinct from those of Java and Borneo, and mark the
furthest eastward range of the genus in the tropics; and two of Eastern
opossums (Cuscus), which are different from those of the Moluccas, and
mark the furthest westward extension of this genus and of the Marsupial
order. Thus we see that the Mammalia of Celebes are no less individual
and remarkable than the birds, since three of the largest and most
interesting species have no near allies in surrounding countries, but
seem vaguely to indicate a relation to the African continent.
Many groups of insects appear to be especially subject to local
influences, their forms and colours changing with each change of
conditions, or even with a change of locality where the conditions seem
almost identical. We should therefore anticipate that the individuality
manifested in the higher animals would be still more prominent in these
creatures with less stable organisms. On the other hand, however, we
have to consider that the dispersion and migration of insects is much
more easily effected than that of mammals or even of birds. They are
much more likely to be carried away by violent winds; their eggs may
be carried on leaves either by storms of wind or by floating trees, and
their larvae and pupae, often buried in trunks of trees or enclosed in
waterproof cocoons, may be floated for days or weeks uninjured over
the ocean. These facilities of distribution tend to assimilate the
productions of adjacent lands in two ways: first, by direct mutual
interchange of species; and secondly, by repeated immigrations of
fresh individuals of a species common to other islands, which by
intercrossing, tend to obliterate the changes of form and colour, which
differences of conditions might otherwise produce. Bearing these facts
in mind, we shall find that the individuality of the insects of Celebes
is even greater than we have any reason to expect.
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