Travel Reference
In-Depth Information
in Mysol, which is equally Papuan in its productions, while either the same, or one closely
allied to it, inhabits New Guinea; but no such animal is found in Ceram, which is only sixty
miles from Mysol. Another small marsupial animal (Perameles doreyanus) is common to
Aru and New Guinea. The insects show exactly the same results. The butterflies of Aru are
all either New Guinea species, or very slightly modified forms; whereas those of Ceram are
more distinct than are the birds of the two countries.
It is now generally admitted that we may safely reason on such facts as these, which sup-
ply a link in the defective geological record. The upward and downward movements which
any country has undergone, and the succession of such movements, can be determined with
much accuracy; but geology alone can tell us nothing of lands which have entirely disap-
peared beneath the ocean. Here physical geography and the distribution of animals and
plants are of the greatest service. By ascertaining the depth of the seas separating one coun-
try from another, we can form some judgment of the changes which are taking place. If
there are other evidences of subsidence, a shallow sea implies a former connexion of the ad-
jacent lands; but if this evidence is wanting, or if there is reason to suspect a rising of the
land, then the shallow sea may be the result of that rising, and may indicate that the two
countries will be joined at some future time, but not that they have previously been so. The
nature of the animals and plants inhabiting these countries will, however, almost always en-
able us to determine this question. Mr. Darwin has shown us how we may determine in al-
most every case, whether an island has ever been connected with a continent or larger land,
by the presence or absence of terrestrial Mammalia and reptiles. What he terms 'oceanic is-
lands' possess neither of these groups of animals, though they may have a luxuriant vegeta-
tion, and a fair number of birds, insects, and land-shells; and we therefore conclude that they
have originated in mid-ocean, and have never been connected with the nearest masses of
land. St. Helena, Madeira, and New Zealand are examples of oceanic islands. They possess
all other classes of life, because these have means of dispersion over wide spaces of sea,
which terrestrial mammals and birds have not, as is fully explained in Sir Charles Lyell's
'Principles of Geology,' and Mr. Darwin's 'Origin of Species.' On the other hand, an island
may never have been actually connected with the adjacent continents or islands, and yet
may possess representatives of all classes of animals, because many terrestrial mammals and
some reptiles have the means of passing over short distances of sea. But in these cases the
number of species that have thus migrated will be very small, and there will be great defi-
ciencies even in birds and flying insects, which we should imagine could easily cross over.
The island of Timor (as I have already shown in Chapter XIII) bears this relation to Aus-
tralia; for while it contains several birds and insects of Australian forms, no Australian
