392 
GEOGEAPHICAL DISTEIBUTIOX. 
Chap. XII. 
shells, across three or four hnndred miles of open sea. 
The different orders of insects in Madeira apparently 
present analogous facts. 
Oceanic islands are sometimes deficient in certain 
classes, and their places are apparently occupied by 
the other inhabitants; in the Galapagos Islands reptiles, 
and in New Zealand gigantic wingless birds, take the 
place of mammals. In the plants of the Galapagos 
Islands, Dr. Hooker has shown that the proportional 
numbers of the different orders are very different from 
what they are elsewhere. Such cases are generally ac¬ 
counted for by the physical conditions of the islands; 
but this explanation seems to me not a little doubtful. 
Facility of immigration, I believe, has been at least as 
important as the nature of the conditions. 
Many remarkable little facts could be given with 
respect to the inhabitants of remote islands. For 
instance, in certain islands not tenanted by mammals, 
some of the endemic plants have beautifully hooked 
seeds ; yet few relations are more striking than the 
adaptation of hooked seeds for transportal by the wool 
and fur of quadrupeds. This case presents no difficulty 
on my view, for a hooked seed might be transported to 
an island by some other means ; and the plant then 
becoming slightly modified, but still retaining its hooked 
seeds, would form an endemic species, having as useless 
an appendage as any rudimentary organ,—for instance, 
as the shrivelled wings under the soldered elytra 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 Can¬ 
dolle has shown, generally have, whatever the cause 
may be, confined ranges. Hence trees would be little 
likely to reach distant oceanic islands; and an herb¬ 
aceous plant, though it would have no chance of 
