ch. ix.] SPECIAL-CREATION, OR DERIVATION? 463 



come a nuisance. But as these animals and their spawn 

 are known to be immediately killed by sea-water, there would 

 be great difficulty in their transportal across the sea, and 

 therefore on my view we can see why they do not exist 

 on any oceanic island. But why, on the theory of creation, 

 they should not have been created there, it would be very 

 difficult to explain." That terrestrial mammals cannot cross 

 the sea is obvious; but bats and birds, which can fly, are 

 found on many oceanic islands. In an admirable essay on 

 the migrations of organisms, considered with reference to the 

 Darwinian theory, Prof. Moritz Wagner has collected many 

 similar examples. From personal observations in North 

 Africa, in Western Asia, in Hungary, and in America, this 

 veteran naturalist educes the general conclusion that the 

 limits within which allied species are found, are determined 

 by impassable natural barriers. Coleoptera with their wings 

 fastened down under their wing-cases, are specifically dif- 

 ferent on the opposite shores of small rivers ; while butterflies 

 and hymenoptera range over large tracts of inland country, 

 but are stopped by such obstacles as the Straits of Gibraltar. 

 On opposite sides of the Andes, the conditions of existence 

 differ but little, while on the north and south sides of the 

 Caucasus the difference in climate is extreme. Yet the 

 Andes are much the more difficult to cross ; and accordingly 

 the fauna which they separate are much more unlike than 

 the fauna separated by the Caucasus. In like manner the 

 Galapagos Islands, situated some six hundred miles from the 

 South American continent, possess a fauna which, with the 

 exception of a few birds, is generically distinct from all other 

 faunas. Yet though generically distinct, it is South Ameri- 

 can in type, and most resembles the fauna of Chili, the 

 nearest mainland. Furthermore, among the animals living 

 on the different islands of the group, we find specific diversity 

 along with generic identity. So also Madeira "is inhabited 

 by a wonderful number of peculiar land-shells, whereas not 



