During this length of time the shell might have been carried by a marine country 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, belonging 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.