328 INHABITANTS OF OCEANIC ISLANDS. [CHAP. XIH. 



their eggs or larvae, perhaps attached to seaweed or floating timber, 

 or to the feet of wading-birds, might be transported across three 

 or four hundred miles of open sea far more easily than laud-shells. 

 The different orders of insects inhabiting Madeira present nearly 

 parallel cases. 



Oceanic islands are sometimes deficient in animals of certain 

 whole classes, and their places are occupied by other classes ; thus 

 in the Galapagos Islands reptiles, and in New Zealand gigantic 

 wingless birds, take, or recently took, the place of mammals. 

 Although New Zealand is here spoken of as an oceanic island, it is 

 in some degree doubtful whether it should be so ranked ; it is of 

 large size, and is not separated from Australia by a profoundly 

 deep sea; from its geological character and the direction of its 

 mountain-ranges, the Rev. W. B. Clarke has lately maintained 

 that this island, as well as New Caledonia, should be considered 

 as appurtenances of Australia. Turning to plants, Dr. Hooker 

 has shown that in the Galapagos Islands the proportional numbers 

 of the different orders are very different from what they are else- 

 where. All such differences in number, and the absence of certain 

 whole groups of animals and plants, are generally accounted for 

 by supposed differences in the physical conditions of the islands ; 

 but this explanation is not a little doubtful. Facility of immigra- 

 tion seems to have been fully as important as the nature of the 

 conditions. 



Many remarkable little facts could be given with respect to the 

 inhabitants of oceanic islands. For instance, in certain islands 

 not tenanted by a single mammal, some of the endemic plants 

 have beautifully hooked seeds ; yet few relations are more mani- 

 fest than that hooks serve for the transportal of seeds in the wool 

 or fur of quadrupeds. But a hooked seed might be carried to an 

 island by other means ; and the plant then becoming modified 

 would form an endemic species, still retaining its hooks, which 

 would form a useless appendage like the shrivelled wings under 

 the soldered wing-covers 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 Candolle 

 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, which had no chance of suc- 

 cessfully competing with the many fully developed trees growing 

 or. a continent, might, when established on an island, gain an 

 advantage over other herbaceous plants by growing taller and 

 taller and overtopping them. In this case, natural selection would 

 tend to add to the stature of the plant, to whatever order it 

 belonged, and thus first convert ir into a bush and then into a 

 tree. 



