implies a former connexion of the adjacent 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 thé 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
enable us to determine this question. Mr. Darwin has
shown us how we may determine in almost every case,
whether an island has ever been connected with a com
tinent or larger land, by the presence or absence of terres-
trial Mammalia and reptiles. What he terms oceanic
islands” piossess neither of these groups of animals, though
they may have a luxuriant vegetation, and a fair number of
birds, insects, and land-shells ; and we therefore conclude
that they havè originated in mid-ocean, and have never
been connected with the nearest masses ©f land. St.
'Helena, Madeira, and Hew 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 deficiencies
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
Australia; for while it contains several birds and insects
of . Australian forms, na Australian mammal or reptile is
found in it, and a great number of the most abundant and
characteristic forms of Australian birds and insects are
entirely absent. Contrast this with the British Islands, in
which a large proportion of the plants, insects, reptiles,
and Mammalia of the adjacent parts of the continent are.
fully represented, while there are. no remarkable deficiencies
of extensive groups, such as .always occur , when
there is reason to believe there has been no such connexion.
The case of Sumatra, Borneo, and Java, and the Asiatic
continent is equally clear ; many large Mammalia, terrestrial
birds, and reptiles being common to all, while a large
number more are of closely, allied forms. . How, geology,
has taught us that this representation by allied forms in
the same locality implies lapse of time, and we therefore
infer that in Great Britain, where almost; every species
is absolutely identical with those "on the Continent, the
separation has been very recent; while in Sumatra and