412 INHABITANTS OF OGBANIG ISLANDS. 



other species are confined to this island and to the Canaries. 

 So that the Islands of Bermuda and Madeira have been 

 stocked from the neighboring continents with birds, which 

 for long ages have there struggled together, and have 

 become mutually co-adapted. Hence, when settled in their 

 new homes, each kind will have been kept by the others to 

 its proper place and habits, and will consequently have 

 been but little liable to modification. Any tendency to 

 modification will also have been checked by intercrossing 

 with the unmodified immigrants, often arriving from the 

 mother-country. Madeira again is inhabited by a wonder- 

 ful number of peculiar land-shells, whereas not one species 

 of sea-shell is peculiar to its shores: now, though we do 

 not know how sea-shells are dispersed, yet we can see that 

 their eggs or larvse, perhaps attached to sea-weed or float- 

 ing tifnber, or to the feet of wading birds, might be trans- 

 ported across three or four hundred miles of open sea far 

 more easily than land-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 mount- 

 ain ranges, the Eev. W. B. Clarke has lately maintained 

 that this island, as well as New Caledonia, should be con- 

 sidered 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 dif- 

 ferent 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 sup- 

 posed differences in the physical conditions of the islands; 

 but this explanation 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 respect 

 to the inhabitanis of oceanic islands. For instance, in 



