OCEANIC ISLANDS. 1 97 



than anywhere else, the generic isolation is equally 

 remarkable. Of the thirty-nine genera twenty-five 

 are peculiar to the island, and many of them such 

 isolated forms that it is impossible to find their 

 allies in any particular country. Even more re- 

 markable is the fact that more than two thirds of 

 the whole number of species belong to one group 

 (Rhyncophora), beetles, which being wood-borers 

 might readily be transported on floating timber 

 for enormous distances. More than two fifths be- 

 long to one family. Of the twenty genera of Rhyn- 

 cophora every one is peculiar to the island, and 

 many have no near allies anywhere else in the world. 

 If possible, still more interesting is the fact that all 

 of these beetles are grouped around a few centres, 

 as if they had only a few points of origin. If seven 

 or eight beetles are assumed to have reached the 

 island and to have given rise to varieties which later 

 became species, this peculiar fauna is explained. 

 The whole of this St. Helena fauna is thus exactly 

 in accordance with the extreme age of the island 

 and its great distance from the mainlands. It is an 

 island so isolated that one bird, a few mollusks, 

 eight or ten individual beetles, and a few plants or 

 reeds, have succeeded in reaching it and establish- 

 ing themselves. Those which did reach the island, 

 however, found such favorable conditions that they 

 rapidly multiplied, and soon gave rise to numerous 

 species, all arranged around several centres, which 

 centres represent the original immigrants. 



The significance of the life on these islands is 

 made stronger when we come to consider other 



