234 Darwin, and after Darwin. 
and, as Sir Joseph Hooker tells us, “cannot be re- 
garded as very close specific allies of any other plants 
at all.” Seventeen of them belong to peculiar genera, 
and the others all differ so markedly as species from 
their congeners, that not one comes under the cate- 
gory of being an insular form of a continental species. 
So that with respect to its plants no less than with 
respect to its animals, we find that the island of 
St. Helena constitutes a little world of unique species, 
allied among themselves, but diverging so much from 
all other known forms that in many cases they con- 
stitute unique genera. 
Sandwich Islands.—These are an extensive group 
of islands, larger than any we have hitherto con- 
sidered—the largest of the group being about the size 
of Devonshire. The entire archipelago is volcanic, 
with mountains rising to a height of nearly 14,000 
feet. The group is situated in the middle of the North 
Pacific, at a distance of considerably over 2,000 miles 
from any other land, and surrounded by enormous 
ocean depths. The only terrestrial vertebrata are 
two lizards, one of which constitutes a peculiar 
genus. There are 24 aquatic birds, five of which are 
peculiar; four birds of prey, two of which are pecu- 
liar; and 16 land-birds, all of which are peculiar. 
Moreover, these 16 land-birds constitute no less 
than 10 peculiar genera, and even one peculiar 
family of five genera. This is an amount of 
peculiarity far exceeding that of any other islands, 
and, of course, corresponds with the great isolation of 
this archipelago. The only other animals which have 
here been carefully studied are the land-shells, and 
these tell the same story as the birds. For there are 
