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ISLAND LIFE. 
[part ii7 
proportion of the St. Helena beetles live evendn the perfect state 
within the stems of plants or trunks of trees, while the eggs 
and larvae of a still larger number are likely to inhabit similar 
stations. Drift-wood might therefore be one of the most 
important agencies by which these insects reached the island. 
Let us now see how far the distribution of other groups sup- 
port the conclusions derived from a consideration of the beetles. 
The Hemiptera have been studied by Dr. F. Buchanan White, 
and though far less known than the beetles, indicate somewhat 
similar relations. Eight out of twenty-one genera are peculiar, 
and the thirteen other genera are for the most part widely 
distributed, while one of the peculiar genera is of African type. 
The other orders of insects have not been collected or studied 
with sufficient care to make it worth while to refer to them 
in detail ; but the land-shells have been carefully collected and 
minutely described by Mr. Wollaston himself, and it is interest- 
ing to see how far they agree with the insects in their 
peculiarities and affinities. 
Land-shells of St. Helena . — The total number of species is 
only twenty-nine, of which seven are common in Europe or the 
other Atlantic islands, and are no doubt recent introductions. 
Two others, though described as distinct, are so closely allied to 
European forms, that Mr. Wollaston thinks they have probably 
even the 300 fathom line, one over 60 miles long; and it is therefore 
probable that a much larger island once occupied this site. Now Ascension 
is nearly equidistant between St. Helena and Liberia, and such an island 
might have served as an intermediate station through which many of the 
immigrants to St. Helena passed. As the distances are hardly greater 
than in the case of the Azores, this removes whatever difficulty may have 
been felt of the possibility of any organisms reaching so remote an island. 
The present island of Ascension is probably only the summit of a huge 
volcanic mass, and any remnant of the original fauna and flora it might 
have preserved may have been destroyed by great volcanic eruptions. Mr. 
Darwin collected some masses of tufa which were found to be mainly 
organic, containing, besides remains of fresh-water infusoria, the siliceous 
tissue of plants ! In the light of the great extent of the submarine bank 
on which the island stands, Mr. Darwin’s remark, that — “we may feel 
sure, that at some former epoch, the climate and productions of Ascension 
were very different from what they are now,” — has received a striking 
confirmation. (See Naturalist's Voyage Round the World, p. 495.) 
