262 HYBERNATION. 



their weakness, and bespeak our sympathy to leave them 

 to repose. Whether the vital functions in these creatures 

 are similarly affected during torpor and hybernation remains 

 to be determined. It is probable that they are. 



In this country, and in others with similar climates, pro- 

 bably all the terrestrial shelled snails, and all the pulmoni- 

 ferous freshwater mollusca, pass the winter in a state of 

 hybernation. I believe that the naked slugs do not hyber- 

 nate ; for, although they retire under stones, clods of earth, 

 or moss, to protect themselves from the cold and storms 

 of the season, yet I have always found them immediately 

 to resume their activity when taken from their conceal- 

 ments, and they are in motion all the winter in mild weather. 

 It is not certainly known, although the contrary has been 

 asserted, * that any marine molluscum hybernates. Some 

 of the littoral species appear to do so. " Mr. Gray found 

 that many individuals of Littorina petraea, and some of 

 Litt. rudis, were in this condition during his stay at 

 Dawlish. They were attached to the rocks several feet 

 above the reach of the highest autumnal tides ; their foot 

 was entirely retracted ; and a membranous film was spread 

 between the rock and the edges of the outer lip of the 

 shell : the gills were only moist, the branchial sac being 

 destitute of that considerable quantity of water which exists 

 in it in those of the same species, which are adherent to 

 the rock by their expanded foot. In this torpid condition, 

 the individuals observed by Mr. Gray continued during the 

 whole of his stay, which lasted for more than a week. On 

 removing several of them and placing them in sea-water, 

 they recovered in a few minutes their full activity." -j- — There 

 would seem to be no necessity that the snails of tropical 

 countries should be endowed with this remarkable property ; 

 but the observations of Adanson prove the contrary. He 

 tells us that the Bulimus Kambeul apparently passes the 

 winter, or dry season, in a deep slumber, like the snails of 

 Europe ; for he found several of them which were half- 

 buried, in the month of September, at the roots of trees 

 and in the thickest brushwoods ; and of these some had 

 already closed the aperture of their shell very exactly with 

 a lid of a whitish and plaster-like matter, to protect them- 

 selves against the long droughts which continue for eight 

 or nine months uninterruptedly. J 



* " The marine mollusca probably migrate in part from the shallower to 

 the deeper waters in cold winters ; many, however, hybernate." — Duncan 

 on the Analogies of Organised Beings, p. 97. t Proc. Zool. Soc. iii. 116. 



+ Hist. Nat. du Senegal, 18. The reader will find some interesting obser- 



