Chap. XIII.] MAMMALS ON OCEANIC ISLANDS. 187 



Would the just-hatclied young sometimes adhere to the 

 feet of bh^ds 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 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 davs in sea-water, and again it recovered and 

 crawled away. Baron Aucapitaine has since tried 

 similar experiments : he placed 100 land-shells, be- 

 longing 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, whicli 

 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 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. 



34 



