308 ISLAND LIFE part ii 



impression is to imagine some mode by which a com- 

 munication between the distant countries implicated 

 might be effected ; and this way of viewing the problem is 

 ahnost universally adopted, even by naturalists. But if 

 the principles laid down in this work and in my Geo- 

 graphical Distribution of Animals are sound, such a course 

 is very unphilosophical. For, on the theory of evolution, 

 nothing can be more certain than that groups now broken 

 up and detached were once continuous, and that frag- 

 mentary groups and isolated forms are but the relics of 

 once w^idespread types, which have been preserved in a few 

 localities where the physical conditions were especially 

 favourable, or where organic competition was less severe. 

 The true explanation of all such remote geographical 

 affinities is, that they date back to a time when the 

 ancestral group of which they are the common descendants 

 had a wider or a different distribution ; and they no more 

 imply any closer connection between the distant countries 

 the allied forms now inhabit, than does the existence of 

 living Equidse in South Africa and extinct Equidae in the 

 Pliocene deposits of the Pampas, imply a continent 

 bridging the South Atlantic to allow of their easy com- 

 munication. 



Concluding Reniarlcs on St, Helena. — The sketch we 

 have now given of the chief members of the indigenous 

 fauna and flora of St. Helena shows, that by means of the 

 knowledge we have obtained of past changes in the 

 physical history of the earth, and of the various modes by 

 which organisms are conveyed across the ocean, all the 

 more important facts become readily intelligible. We 

 have here an island of small size and great antiquity, very 

 distant from every other land, and probably at no time 

 very much less distant from surrounding continents, 

 which became stocked by chance immigrants from other 

 countries at some remote epoch, and which has preserved 

 many of their more or less modified descendants to the 

 present time. When first visited by civilised man it was 

 in all probability far more richly stocked with plants and 

 animals, forming a kind of natural museum or vivarium in 

 which ancient types, perhaps dating back to the Miocene 



