EVIDENCES FROM GEOGRAPHIC DISTRIBUTION 109 



referred to three types ; the 1 1 species of Bemhidium form a group by 

 themselves; and the Heteromera form two groups. ''Now, each of 

 these types may well be descended from a single species, which origi- 

 nally reached the island from some other land; and the great variety 

 of generic and specific forms into which some of them have diverged 

 is an indication, and to some extent a measure, of the remoteness of 

 their origin" [Wallace]. But, on the counter-supposition that all these 

 128 peculiar species were separately created to occupy this particular 

 island, it is surely unaccountable that they should thus present 

 such an arborescence of natural affinities amongst themselves. 



Passing over the rest of the insect fauna, which has not yet been 

 sufficiently worked out, we next find that there are only 20 species of 

 indigenous land-shells — which is not surprising when we remember by 

 what enormous reaches of ocean the land is surrounded. Of these 20 

 species no less than 13 have become extinct, three are allied to Euro- 

 pean species, while the rest are so highly peculiar as to have no near 

 allies in any other part of the globe. So that the land-shells tell 

 exactly the same story as the insects. 



Lastly, the plants likewise tell the same story. The truly indige- 

 nous flowering plants are about 50 in number, besides 26 ferns. Forty 

 of the former and ten of the latter are peculiar to the island, and, as 

 Sir Joseph Hooker tells us, "cannot be regarded 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 category 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 constitute unique genera. 



Sandwich Islands. — These are an extensive group of islands, 

 larger than any we have hitherto considered — the largest of the group 

 being about the size of Devonshire. The entire archipelago is vol- 

 canic, 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 vertebrates 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 peculiar; and 16 land-birds, all of which are peculiar. 



