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- 

 sideredthe 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 1 6 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 



