skin on each side of the snout, curving backwards to near the eyes, and in old
animals often reaching eight or ten inches in length. It is difficult to understand
what can be the use of these extraordinary horn-like teeth. Some of the old
writers supposed that they served as hooks, by which the creature could rest its
head on a branch. But the way in which they usually diverge just over and in
front of the eye has suggested the more probable idea, that they serve to guard
these organs from thorns and spines, while hunting for fallen fruits among the
tangled thickets of rattans and other spiny plants. Even this, however, is not
satisfactory, for the female, who must seek her food in the same way, does not
possess them. I should be inclined to believe rather, that these tusks were once
useful, and were then worn down as fast as they grew; but that changed
conditions of life have rendered them unnecessary, and they now develop into a
monstrous form, just as the incisors of the Beaver or Rabbit will go on growing,
if the opposite teeth do not wear them away. In old animals they reach an
enormous size, and are generally broken off as if by fighting.
Here again we have a resemblance to the Wart-hogs of Africa, whose upper
canines grow outwards and curve up so as to form a transition from the 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