INHABITANTS OF ISLANDS 439 



it and are killed. Yet there must be some unknown, but 

 occasionally efficient means for their transportal. Would the 

 just-hatched young sometimes adhere to the feet of birds 

 roosting on the ground, and thus get transported? It oc- 

 curred to me that land-shells, when hybernating and having a 

 membranous diaphragm over the mouth of the shell, might 

 be floated in chinks of drifted timber across moderately wide 

 arms of the sea. And I find that several species in this state 

 withstand uninjured an immersion in sea- water during seven 

 days : one shell, the Helix pomatia, after having been thus 

 treated and again hybernating was put into sea-water for 

 twenty days, and perfectly recovered. During this length of 

 time the shell might have been carried by a marine current 

 of average swiftness, to a distance of 660 geographical miles. 

 As this Helix has a thick calcareous operculum. I removed 

 it, and when it had formed a new membranous one, I again 

 immersed it for fourteen days in sea-water, and again it 

 recovered and crawled away. Baron Aucapitaine has since 

 tried similar experiments ; he placed 100 land-shells, belong- 

 ing to ten species, in a box pierced with holes, and immersed 

 it for a fortnight in the sea. Out of the hundred shells, 

 twenty-seven recovered. The presence of an operculum 

 seems to have been of importance, as out of twelve specimens 

 of Cyclostoma elegans, which is thus furnished, eleven re- 

 vived. It is remarkable, seeing how well the Helix pomatia 

 resisted with me the salt-water, that not one of fifty-four 

 specimens belonging to four other species of Helix tried by 

 Aucapitaine, recovered. It is, however, not at all probable 

 that land-shells have often been thus transported ; the feet 

 of birds offer a more probable method. 



ON THE RELATIONS OF THE INHABITANTS OF ISLANDS TO 

 THOSE OF THE NEAREST MAINLAND 



The most striking and important fact for us is the affinity 

 of the species which inhabit islands to those of the nearest 

 mainland, without being actually the same. Numerous in- 

 stances could be given. The Galapagos Archipelago, situ- 

 ated under the equator, lies at the distance of between 500 

 and 600 miles from the shores of South America. Here 



