10 ON THE LAW WHICH HAS REGULATED 



pagos Islands, which contain littte groups of plants 

 and animals peculiar to themselves, but most nearly 

 allied to those of South America, have not hither- 

 to received any, even a conjectural explanation. 

 The Galapagos are a volcanic group of high anti- 

 quity, and have probably never been more closely 

 connected with the continent than they are at 

 present. They must have been first peopled, like 

 other newly-formed islands, by the action of winds 

 and currents, and at a period sufficiently remote 

 to have had the original species die out, and the 

 modified prototypes only remain. In the same way 

 we can account for the separate islands having each 

 their peculiar species, either on the supposition that 

 the same original emigration peopled the whole of 

 the islands with the same species from which differ- 

 ently modified prototypes were created, or that the 

 islands were successively peopled from each other, 

 but that new species have been created in each on 

 the plan of the pre-existing ones. St. Helena is a 

 similar case of a very ancient island having obtained 

 an entirely peculiar, though limited, flora. On the 

 other hand, no example is known of an island which 

 can be proved geologically to be of very recent 

 origin (late in the Tertiary, for instance), and yet 

 possesses generic or family groups, or even many 

 species peculiar to itself. 



When a range of mountains has attained a great 

 elevation, and has so remained during a long geolo- 

 gical period, the species of the two sides at and 



