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Show 392 GEOGRAPHICAL DISTRIBUTION. what they are elsewhere. Such c~~es are genei:ally accounted for by the physical conditions o~ the Islands; but this explanation seems to me not a httle doubtful. Facility of immigration, I believe, ~a.s been at least as important as the nature of the conditions. . . Many remarkable little facts could b~ given with respect to the inhabitants of remote Islands. For instance, in certain islands not tenanted by mammals, some of the endemic plants have beautifully hooked seeds ; yet few relations are more striking than the adaptation of hooked seeds for transportal by the wool and fur of quadrupeds. This case presents no difficulty on my view, for a hooked seed might be traneported to an island by some other means; and the plant then becoming slightly modified, but still retaining its hooked seeds, would form an endemic species, having as useless an appendage as any rudimentary organ,-for instance, as the shrivelled wings under the soldered elytra of many insular beetles. Again, islands often possess trees or bushes belonging to orders which elsewhere include only herbaceous species; now trees, as Alph. de Oandolle has shown, generally have, whatever the cause may be, confined ranges. Hence trees would be little likely to reach distant oceanic islands; and an herbaceous plant, though it would have no chance of successfully competing in stature with a fully de:eloped tree, when established on an island and havmg to compete with herbaceous plants alone, might readily gain an advantage by growing taller and taller ~nd overtopping the other plants. If so, natural selectiOn would often tend to add to the stature of herbaceous plants when growing on an island, to whatever order they belonged, and thus convert them first into bushes and ultimately into trees. With respect to the absence of whole orders on CIIAP. XII. OOEANIO ISLANDS. 393 oceanic islan~s, Bory St. Vincent long ago remarked that Batrachians (frogs, toads, newts) have never been found on any of the many islands with which the great ocean~ are studded. I have taken pains to verify this assertion, and I have found it strictly true. I have, ho.wever, been assured that a frog exists on the mountains o~ the grea.t isl~nd of .New Zealand; but I suspect that this .exception (if the Information be correct) may be explained through glacial agency. This general ~bsence of frogs, toads, and newts on so many oceanic IS~~nds c~nnot b~ accounted for by their physical conditiOns; Indeed It .seems that islands are peculiarly well ~tted for t~ese animals; for frogs have been introduced Into .M~deua, the Azores, and Mauritius, and have m~tiphed so as to become a nuisance. But as these a~Imals and their spawn are known to be immediately killed by sea-water, on my view we can see that there would be great difficulty in their transportal across the. s~a, and therefore why they do not exist on any oceanic Island. But why, on the theory of creation they s~ould not have been created there, it would b~ very difficult to explain. Mammals offer another and similar case. I have ca~efully searched the oldest voyages, but have not ~nished my search; as yet I have not found a single Instanc~, free from doubt, of a terrestrial mammal ~excl~~ng do~esticated animals kept by the natives) Inha?Iting an Island situated above 300 miles from a c?ntlnent or great continental island; and many islands Situated at a much less distance are equally barren. ~he Falkland Islands, which are inhabited by a wolf- Ike fox, come .nearest to an exception; but this group cannot be considered as oceanic, as it lies on a bank con~ ected with the mainland; moreover, icebergs formerly rought boulders to its western shores, and they may s 3 |