MAMMALS ON OCEANIC ISLANDS. 389 



lo a continent ; and hardly an island can be named on which 

 our smaller quadrupeds have not become naturalized and 

 greatly multiplied. It cannot be said, on the ordinary view 

 of creation, that there has not been time for the creation of 

 mammals ; man}'- volcanic islands are sufficiently ancient, as 

 shown by the stupendous degradation which they have suf- 

 fered, and by their tertiary strata: there has also been time 

 for the production of endemic species belonging to other 

 classes ; and on continents it is known that new species of 

 mammals appear and disappear at a quicker rate than other 

 and lower animals. Although terrestrial mammals do not 

 occur on oceanic islands, aerial mammals do occur on almost 

 every island. New Zealand possesses two bats found nowhere 

 else in the world : Norfolk Island, the Viti Archipelago, the 

 Bonin Islands, the Caroline and Marianne Archipelagoes, 

 and Mauritius, all possess their peculiar bats. Why, it may 

 be asked, has the supposed creative force produced bats and 

 no other mammals on remote islands ? On my view this 

 question can easily be answered; for no terrestrial mammal 

 can be transported across a wide space of sea, but bats can 

 fly across. Bats have been seen wandering by day far over 

 the Atlantic Ocean ; and two North American species, either 

 regularly or occasionally, visit Bermuda, at the distance of 

 600 miles from the mainland. I hear from Mr. Tomes, who 

 has specially studied this family, that many species have 

 enormous ranges, and are found on continents and on far 

 distant islands. Hence, we have only to suppose that such 

 wandering species have been modified in their new homes in 

 relation to their new position, and we can understand the 

 presence of endemic bats on oceanic islands, with the 

 absence of all other terrestrial mammals. 



Another interesting relation exists, namely, between the 

 depth of the sea separating islands from each other, or from 

 the nearest continent, and the degree of affinity of their mam 

 malian inhabitants. Mr. Windsor Earl has made some strik- 

 ing observations on this head, since greatly extended b) T Mr. 

 Wallace's admirable researches, in regard to the great Malay 

 Archipelago, which is traversed near Celebes by a space of 

 deep ocean, and this separates two widely distinct mam- 

 malian faunas. On either side, the islands stand on a mod- 

 erately shallow submarine bank, and these islands are 

 inhabited by the same or by closely allied quadrupeds. I 

 have not as yet had time to follow up this subject in all 

 quarters of the world j but as far as I have gone, the relar 



