284 



ISLAND LIFE 



PART II 



the theory of the peopling of the islands by accidental 

 migrations, if we only allow them to have existed for a 

 sufficiently long period ; and the fact that volcanic action 

 has ceased on many of the islands, as well as their great 

 extent, would certainly indicate a considerable antiquity. 



The great difference presented by the birds of these 

 islands as compared with those of the equally remote 

 Azores and Bermudas, is sufficiently explained by the 

 difference of climatal conditions. At the Galapagos there 

 are none of those periodic storms, gales, and hurricanes 

 which prevail in the North Atlantic, and which every 

 year carry some straggling birds of Europe or North 

 America to the former islands ; while, at the same time, 

 the majority of the tropical American birds are non- 

 migratory, and thus afford none of the opportunities 

 presented by the countless hosts of migrants which pass 

 annually northward and southward along the European, 

 and especially along the North American coasts. It is 

 strictly in accordance with these different conditions that 

 we find in one case an almost perfect indentity with, and 

 in the other an almost equally complete diversity from, 

 the continental species of birds. 



Insects and Land-shells. — The other groups of land- 

 animals add little of importance to the facts already 

 referred to. The insects are very scanty; the most 

 plentiful group, the beetles, only furnishing about forty 

 species belonging to thirty-two genera and nineteen 

 families. The species are almost all peculiar, as are some 

 of the genera. They are mostly small and obscure insects, 

 allied either to American or to world-wide groups. The 

 Carabidse and the Heteromera are the most abundant 

 groups, the former furnishing six and the latter nine 

 species.^ 



The land-shells are not abundant — about forty-six in all, 

 belonging to ten genera, but two-thirds of the whole are 

 Bulimuli, and there is no peculiar genus, although almost 



^ The following list of the beetles yet known from the Galapagos show 

 their scanty proportions and accidental character ; the forty species be- 

 longing to thirty-three genera and eighteen families. It is taken from 

 Mr. Waterhouse's enumeration in the Proceedings of the Zoological Society 



