GEOGRAPHICAL DISTRIBUTION 353 



to compete with herbaceous plants alone, might readily 

 gain an advantage by growing taller and taller and 

 overtopping the other plants. If so, natural selection 

 would often tend to add to the stature of herbaceous 

 plants when growing on an oceanic island, to whatever 

 order they belonged, and thus convert them first into 

 bushes and ultimately into trees. 



With respect to the absence of whole orders on 

 oceanic islands, Bory St. Vincent long ago remarked 

 that Batrachians (frogs, toads, newts) have never been 

 found on any of the many islands with which the great 

 oceans are studded. I have taken pains to verify this 

 assertion, and I have found it strictly true. I have, 

 however, been assured that a frog exists on the moun- 

 tains of the great island of New Zealand ; but I suspect 

 that this exception (if the information be correct) may 

 be explained through glacial agency. This general 

 absence of frogs, toads, and newts on so many oceanic 

 Islands cannot be accounted for by their physical con- 

 ditions ; indeed it seems that islands are peculiarly well 

 fitted for these animals ; for frogs have been introduced 

 into Madeira, the Azores, and Mauritius, and have 

 multiplied so as to become a nuisance. But as these 

 animals and their spawn are known to be immediately 

 killed by sea-water, on my view we can see that there 

 would be great difficulty in their transportal across 

 the sea, and therefore 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. 



Mammals offer another and similar case. I have 

 carefully searched the oldest voyages, but have not 

 finished my search ; as yet I have not found a single 

 instance, free from doubt, of a terrestrial mammal 

 (excluding domesticated animals kept by the natives) 

 inhabiting an island situated above 300 miles from a 

 continent or great continental island ; and many islands 

 situated at a much less distance are equally barren. 

 The Falkland Islands, which are inhabited by a wolf- 

 like fox, come nearest to an exception ; but this group 



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