190 THE ORIGIN OF SPECIES 



of certain whole classes, and tlieir places are occupied 

 by other classes; thus in the Galapagos Islands rejttihis, 

 and in New Zealand gigantic wingless birds, take, or 

 recently took, the place of mammals. Althougii 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 elsewhere. 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 exjlaiia- 

 tion is not a little doubtful. Facility of immigration 

 seems to have been fully as important as the nature 

 of the conditions. 



Many remarkable little facts could be given with re- 

 spect 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 manifest than that hooks serve 

 for the transportal of seeds in the wool or fur of quadru- 

 peds. 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 



