104 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
only terrestrial Vertebrate (unless the rats and mice are indigenous) 
is a lizard allied to an American form, but specifically distinct from it, 
and therefore a solitary species which does not occur anywhere else in 
the world. None of the birds or bats are peculiar, any more than in 
the case of the Azores; but, as in that case, a large percentage of the 
land-shells are so—namely, at least one quarter of the whole. Neither 
the botany nor the entomology of this group has been worked out; 
but I have said enough to show how remarkably parallel are the cases 
of these two volcanic groups of islands situated in different hemispheres 
but at about the same distance from large continents. In both there 
is an extraordinary paucity of terrestrial Vertebrata, and of any 
peculiar species of bird or beast. On the other hand, there is in both 
a marvellous wealth of peculiar species of insects and land-shflls. 
Now these correlations are all abundantly intelligible. It is a difficult 
matter for any terrestrial animal to cross goo, or even 700 miles of 
ocean: therefore only one lizard has succeeded in doing so in one of the 
two parallel cases; and living cut off from intercrossing with its 
parent form, the descendants of that lizard have become modified so as 
to constitute a peculiar species. But it is more easy for large flying 
animals to cross those distances of ocean: consequently, there is only 
one instance of a peculiar species of bird or bat—namely, a bull-finch 
in the Azores, which, being a small land-bird, is not likely ever to have 
had any other visitors from its original parent species coming over 
from Europe to keep up the original breed. Lastly, it is very much more 
easy for insects and land-mollusca to be conveyed to such islands by 
wind and floating timber than it is for terrestrial mammals, or even 
than it is for small birds and bats; but yet such means of transit are 
not sufficiently sure to admit of much recruiting from the mainland 
for the purpose of keeping up the specific types. Consequently, the 
insects and the land-shells present a much greater proportion of 
peculiar species—namely, one half and one fourth of the land-shells in 
the one case, and one eighth of the beetles in the other. All these cor- 
relations, I say, are abundantly intelligible on the theory of evolution; 
but who shall explain, on the opposite theory, why orders of beetles 
‘and land-mollusca should have been chosen from among all other 
animals for such superabundant creation on oceanic islands, so that 
in the Azores alone we find no less than 32 of the one and 14 of the 
other? And, in this connection, I may again allude to the peculiar 
species of beetles in the island of Madeira. Here there are an enor- 
mous number of peculiar species, though they are nearly all related to, 
