OCR Text |
Show 342 GEOGRAPHICAL DISTRIBUTION. [CHAP. XII. islands often possess trees or b us h es belonging t.o o. rders w hI.C 1 1 e1 s ew h ere I. nc lude only herbaceous spec1i1e s' hn ow trees as Alph de Candolle has shown, geneHra Y ave, what'e ver the c·a use may b e, con fin e d r·a n ao- es · . en. ce trees would be little likely to reach distant oceanic Islands ; d h b Olls Plant thoua-h it would have no chance an an er ace ' o . f 11 d 1 d of successfully cOinpeting in sta~ure With a u J: eve ope tree ·w·hen established on an Island .and havi?-g to .compet~ with herbaceous plants alone, might readily gain. an advantage by growing taller and tal~er and overtopping the other plants. If so, natural selection would often t~nd to add to the stature of herbaceous plants when growing on an island, to whatever order they.belonge~, and thus convert them first into bushes and ultnnately Into trees .. With respect to ~he absence of whole o:·ders on ocea~IC islands, Bory St. VIncent long ago remailred that Batiachians (frogs, toads, newts) h.ave never been found on any of the many islands with wlnch tl~e gre~t ocean~ are studded. I have taken pains to verify tlns assertion, and I have found it strictly true. I have, ho:vever, been assured that a frog exists on the mountains ~f the gr~at island of New Zealand ; but I suspect that t!ns exceptiOn (if the information be correct) 1nay be ex~lained through glacial agency. This general absence of frogs, toads, and newts on so many ocean~c isla~ds can~ot be accoun.ted for by their physical conditions; 1ndeed It seems that Islands are peculiarly well fitted for these animals ; for frogs ha~.e been introduced into Madeira, the Azores, and ~aunt' s and have multiplied ao as to becoine a nuisance. ~~t as these animals and their spawn a;·e known to be immediately killed. by sea-water, on 1ny v1e:w we can see that there would be great difficulty in thmr t:ansportal across the sea, and therefore why they do not ex1~t on ~ny oceanic island. But why, on the theorJ: of creation, t ~y should not have been created there, It would be veiy difficult to explain. . . Mammals offer another and similar case. I have .chid fully searched the oldest voyages, but .have. not finlsf e my search · as yet I have not found a single !?stance, r:.e from doubt, of' a terrestrial ma1nmal (excluding domes I-CHAP. XII.] OCEANIC ISLANDS. 343 c~ted animals kept by. the natives) inhabiting an island s.i tuatte d1 . a1b ovde 300d miles f.r om a continent or oa- reat con- tnlen a IS an ; an many Islands situated at a much Ie distance are equally barren. The Falkland Islands whi:h a;e inhabited. by a wolf-like fox, come nearest to an' excep~ w:r; ; but this group cannot. be considered as oceanic, as It hes on a bank connected With the mainland· moreover icebergs formerly brought boulders to its western shores' ·and they may have formerly transported foxes as so fre~ quently now hapfens in the arctic regions. Yet it cannot be said that s~.al islands will not support small mammals, ror they. OCCUr Ill many )?arts of the world on very small Islands, If close to a continent ; and hardly an island can be named on which our smaller quadrupeds have not become natural~sed an~ greatly m~Iltiplied. It cannot be said, on the ordinary.view of creation, that there has not been time for the creation of mammals ; many volcanic islands are s~:rfficie~tly ancient, as shown by tho stupendous degradation whiCh they have suffered and by their tertiary strata : ther~ has also _been time for the production of endemic species belonging/to other classes; and on continents it is thought that mammals appear ~nd disappear at a quicker rate than other and lower animals. Though terrestrial mammals do not occur on oceanic islands aerial mammals do occur on almost every island. New Zealand possesses two bats found nowhere else in the world : Norfolk Island the Viti Archipelago, the Bonin Islands the Caroline and Mari~lffie Archipelago.es, and Mauritiu;, all possess their · pecu~Iar bats. Why, It may be asked, has the supposed creative .. force produced bats and no other mammals on remote Islands ? On my view this question can easily be answered;. for no terrestrial mammal can be transported across a Wide space of sea, but bats can fly across. Bats have been seen wandering by day far over the Atlantic Ocean; .and two .~orth American species either regularly or occasiOnally VISit Bermuda at the distance of 600 miles fro~ the p1ainland. I hear 'from Mr. Tomes, who has specially studied this family, that n1any of the same speCies have en?rmous. ranges, and are found on continents and on far distant Islands. Hence we have only to sup- |