ABSENCE OF BATRACHIANS 435 



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 inhabitants of oceanic islands. For instance, in cer- 

 tain islands not tenanted by a single mammal, some of the 

 endemic plants have beautifully hooked seeds; yet few rela- 

 tions are more manifest than that hooks serve for the trans- 

 portal of seeds in the wool or fur of quadrupeds. 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 beetles. Again, islands often possess 

 trees or bushes belonging to orders which elsewhere include 

 only herbaceous species ; now trees, as Alph. de Candolle 

 has shown, generally have, whatever the cause may be, con- 

 fined ranges. Hence trees would be little likely to reach dis- 

 tant oceanic islands ; and an herbaceous plant, which had no 

 chance of successfully competing with the many fully devel- 

 oped trees growing on a continent, might, when established 

 on an island, gain an advantage over other herbaceous plants 

 by growing taller and taller and overtopping them. In this 

 case, natural selection would tend to add to the stature of the 

 plant, to whatever order it belonged, and thus first convert 

 it into a bush and then into a tree. 



ABSENCE OF BATRACHIANS AND TERRESTRIAL MAMMALS ON 

 OCEANIC ISLANDS. 



With respect to the absence of whole orders of animals on 

 oceanic islands, Bory St. Vincent long ago remarked that 

 Batrachians (frogs, toads, newts) are never found on any of 

 the many islands with which the great oceans are studded. 

 I have taken pains to verify this assertion, and have found 

 it true, with the exception of New Zealand, New Caledonia, 

 the Andaman Islands, and perhaps the Salomon Islands and 

 the Seychelles. But I have already remarked that it is 

 doubtful whether New Zealand and New Caledonia ought to 

 be classed as oceanic islands; and this is still more doubtful 

 with respect to the Andaman and Salomon groups and the 



