have descended from a single parent; and therefore have all proceeded
from a common birthplace, notwithstanding that in the course of time
they have come to inhabit distant points of the globe. I have already
stated that I cannot honestly admit Forbes s view on continental
extensions, which, if legitimately followed out, would lead to the
belief that within the recent period all existing islands have been
nearly or quite joined to some continent. This view would remove many
difficulties, but it would not, I think, explain all the facts in
regard to insular productions. In the following remarks I shall not
confine myself to the mere question of dispersal; but shall consider
some other facts, which bear on the truth of the two theories of
independent creation and of descent with modification.
The species of all kinds which inhabit oceanic islands are few in
number compared with those on equal continental areas: Alph. de
Candolle admits this for plants, and Wollaston for insects. If we look
to the large size and varied stations of New Zealand, extending over
780 miles of latitude, and compare its flowering plants, only 750 in
number, with those on an equal area at the Cape of Good Hope or in
Australia, we must, I think, admit that something quite independently
of any difference in physical conditions has caused so great a
difference in number. Even the uniform county of Cambridge has 847
plants, and the little island of Anglesea 764, but a few ferns and a
few introduced plants are included in these numbers, and the comparison
in some other respects is not quite fair. We have evidence that the
barren island of Ascension aboriginally possessed under half-a-dozen
flowering
plants; yet many have become naturalised on it, as they have on New
Zealand and on every other oceanic island which can be named. In St.
Helena there is reason to believe that the naturalised plants and
animals have nearly or quite exterminated many native productions. He
who admits the doctrine of the creation of each separate species, will
have to admit, that a sufficient number of the best adapted plants and
animals have not been created on oceanic islands; for man has
unintentionally stocked them from various sources far more fully and
perfectly than has nature.
Although in oceanic islands the number of kinds of inhabitants is
scanty, the proportion of endemic species (_i.e._ those found nowhere
else in the world) is often extremely large. If we compare, for
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