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Show 390 GEOGRAPHICAL DISTRIBUTION. CHAP. XII. 1 t t any have become naturalised on it, pans; ye m as they have on New Zealand and on every other oceaniC· I·S 1 a n d whi'ch can be named. In S. t. Helena th ere I·S reason to beli'eve that the natura.l ised plants and animals have nearly or quite ?xterminated .many native productions. He who adm1t~ the .doctnne of the creation of each separate spemes, will have to a d1 n'it, that a sufficient number of the best adapte.d 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 n~mber of kinc~s of inhabitants is scanty, the proportion of endemic species (i.e. those found nowhere else in th~ world) is often extremely large. If we compare, for Instance, the number of the endemic land-shells in Madeira, or of the endemic birds in the Galapagos Archipelago, with the number found on any continent, and then compare the area of the islands with that of the continent, we shall see that this is true. This fact might have been expected on my theory, for, as alre~dy explai~ed, species occasionally arriving after long Intervals I~ a new and isolated district, and having to compete with new associates, will be eminently liable to modification, and will often produce groups of modified descendants. But it by no means follows, that, because. in an island nearl~ all the species of one class are peculiar, those of another class, or of another section of the same class, are pe~uliar · and this difference seems to depend on the spec~es whi~h do not become modified having immigrated ';Ith facility and in a body, so that their mutual relatwns have not been much disturbed. Thus in the Galapagos Islands nearly every land-bird, but only two o~t ofthh et ul. d "t · bvwus t a eleven marine birds, are pee Iar ; an I IS o CIIAP. XII. OCEANIC ISLANDS. 39 1 marine birds could arrive at these islands more easilyth land-birds. Bermuda, on the other hand, which lies:~ about the same distance from North America as the Galapagos Islands do from South America, and which has a :ery peculiar soil, does not possess one endemic land bud ; and we know from Mr. J. M. Jones's admirab~ e acc?unt of .Bermuda, that very many North ~~eriC~n birds, ~m:1ng their great annual migrations, VISit . either penod1eally or occasionally this island. Madeua does not possess one peculiar bird, and many European and African birds are almost every year blown there, as I am informed by Mr. E. V. Harcou1 t. So that these two islands of Bermuda and Madeira have been stocked ~y birds, which for long ages have struggled together In their former homes, and have become mutually adapted to each other; and when settled in their new h?mes, each kind will have been kept by the others to their proper p~aces and habits, and will consequently have been httle hable to modification. Madeira again is inhabited by a wonderful number of peculia~ land~ ~hells, where as not one species of sea-shell is confined to Its sh?res : now, though we do not know how sea-shells are dispersed, yet we can see that their eggs or larvre, perhaps attach~d to. seaweed or floating timber, or to the. feet of wading-buds, might be transported far more ea.sily than land-shells, across three or four hundred miles of open sea. The different orders of insects in Madeira .ap~arently present analogous facts. Ocearuc Islands are sometimes deficient in certain classes, a~d th~ir places are apparently occupied by the o~her Inhabitants; in the Galapagos Islands reptiles, and In New Zealand gigantic wingless birds, take the place of mammals. In the plants of the Galapagos Islands, Dr. I-Iooker has shown that the proportional numbers of the different orders are very different from |