CHAP. XIII THE GALAPAGOS ISLANDS 285 



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

 most of them peculiar species, but not otherwise remark- 

 fuble. The observation of Captain Collnet, quoted by Mr. 

 Darwin in his Journal, that drift-wood, bamboos, canes, 

 and the nuts of a palm, are often washed on the south- 

 eastern shores of the islands, furnishes an excellent clue 

 to the manner in which many of the insects and land- 

 shells may have reached the Galapagos. Whirlwinds also 

 have been known to carry quantities of leaves and other 

 vegetable dehris to great heights in the air, and these 

 might be then carried away by strong upper currents and 

 dropped at great distances, and with them small insects 

 and mollusca, or their eggs. We must also remember 

 that volcanic islands are subject to subsidence as well as 

 elevation ; and it is quite possible that during the long 

 period the Galapagos have existed some islands may have 

 intervened between them and the coast, and have served 

 as stepping-stones by which the passage to them of 

 various organisms would be greatly facilitated. Sunken 

 banks, the relics of such islands, are known to exist in 

 many parts of the ocean, and countless others, no doubt, 

 remain undiscovered. 



The Keeling Islands as Illustrating the Manner in wliieli 

 Oceanic Islctnds cere Peopled. — That such causes as have 

 been here adduced are those by which oceanic islands have 

 been peopled, is further shown by the condition of equally 

 remote islands which we know are of comparatively recent 

 origin. Such are the Keeling or Cocos Islands in the 

 Indian Ocean, situated about the same distance from 

 Sumatra as the Galapagos from South America, but mere 

 coral reefs, supporting abundance of cocoa-nut palms as their 

 chief vegetation. These islands were visited by Mr. 



CURCULIOXID/E. PhYTOPHAGA 



Otiorhynchus cuneiformis. Diabrotica limbata. 



Anchonus galapagoensis. Docema galapagoensis. 



LoNGicoPtNiA. Longitarsus lunatus, 

 Mallodou sp. Securipalpes. 



Eburia amabilis. Scymuns galapagoensis. 



A NTHRIBID^, 



Ormiscus variegatus. 



