ds,
we have the peculiar wingless forms alluded to in a previous chapter
(viz. that on Morphology); and, without waiting to go into details, it
is notorious that the faunas of Australia and New Zealand are not only
highly peculiar, but also suggestively archaic. Therefore, in both the
respects above mentioned, the anticipations of our theory are fully
borne out. But as it would take too long to consider, even cursorily,
the faunas and floras of these immense islands, I here allude to them
only for the sake of illustration. In order to present the argument from
geographical distribution within reasonable limits, I think it is best
to restrict our examination to smaller areas; for these will better
admit of brief and yet adequate consideration. But of course it will be
understood that the less isolated the region, and the shorter the time
that it has been isolated, the smaller amount of peculiarity should we
expect to meet with on the part of its present inhabitants. Or,
conversely stated, the longer and the greater the isolation, the more
peculiarity of species would our theory expect to find. The object of
the present chapter will be to show that these, and other cognate
expectations, are fully realized by facts; but, before proceeding to do
this, I must say a few words on the antecedent standing of the argument.

Where the question is, as at present, between the rival theories of
special creation and gradual transmutation, it may at first sight well
appear that no test can be at once so crucial and so easily applied as
this of comparing the species of one geographical area with those of
another, in order to see whether there is any constant correlation
between differences of type and degrees of separation. But a little
further thought is enough to show that the test is not quite so simple
or so absolute--that it is a test to be applied in a large and general
way over the surface of the whole earth, rather than one to be relied
upon as exclusively rigid in every special case.

In the first place, there is the obvious consideration that lands or
seas which are discontinuous now may not always have been so, or not for
long enough to admit of the effects of separation having been exerted to
any considerable extent upon their inhabitants. Next, there is the
scarcely less important consideration, that although land areas may long
have been separated from one another by extensive tracts of ocean,
birds and insects may more o