Geographical Distribution. 233 
is due to high antiquity is further indicated, accord- 
ing to our theory, by the large number of species which 
some of the types comprise. Thus, the 54 species of 
Cossonide may be referred to three types; the 11 
species of Bembidinm 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 originally 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.” But, 
on the counter-supposition that all these 128 pecu- 
liar 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 island is surrounded. 
Of these 20 species no less than 13 have become 
extinct, three are allied to European 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 indigenous flowering plants are about 50 
in number, besides 26 ferns. Forty of the former 
and ten of the latter are peculiar to the island, 
1 Wallace, Zsland Life, p. 287. 
