Chap. XUI.] MAMMALS ON OCEANIC ISLANDS. 187 



hatched young sometimes adhere to the feet of birds 

 roosting on the ground, and thus get transported? It 

 occurred 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 geo- 

 graphical miles. As this HeUx has a thick calcareous 

 operculum, I removed it, and when it had formed a 

 new membranous one, I again immersed it for four- 

 teen days in sea-water, and again it recovered and 

 crawled away. Baron Aucapitaine has since tried simi- 

 lar experiments: he placed 100 land-shells, belonging 

 to ten species, in a box pierced with holes, and im- 

 mersed it for a fortnight in the sea. Out of the hun- 

 dred 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 revived. It is remarkable, 

 seeing how well the Helix pomatia resisted with me the 

 salt-water, that not one of fifty-four specimens be- 

 longing to four other species of HeUx tried by Aucapi- 

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

 that land-shells have often been thus transported; the 

 feet of birds ofPer a more probable method. 



