i 1 6 Natural History of Molluscous Animals : — 



du Senegal, p. 7.) The latter supposition is the only one 

 which can, I think, solve the question. 



When in this torpid state, the condition of the snail itself 

 has not been ascertained. Some authors speak of it as being 

 dormant^ and the language would seem to imply that they 

 consider it in a state of sleep, in which the circulation and re- 

 spiration go on uninterruptedly and as strongly as when awake ; 

 but I suspect that the authors alluded to never intended that 

 such an inference should be drawn from their analogical lan- 

 guage. The fact is, it is not known precisely whether the 

 circulation goes on or is stopped, or whether the contact of air 

 is essential or otherwise. It is difficult to believe that all the 

 functions as well as the signs of life cease entirely ; and yet 

 it is scarcely less so to suppose that, for the space of fifteen 

 years or more, those functions could exist without some supply 

 of food to keep up the waste and secretions, however trivial, 

 which necessarily flow from a circulation, or without some air 

 to purify the circulating fluid.* 



If I deem it necessary to distinguish torpidity from sleep, 

 it is, perhaps, not less so to distinguish it from the state of 

 hybernation, although the phenomena of both are more 

 strictly analogous. Snails become torpid when the atmosphere 

 is hot and dry ; and, as often as they are unbound by the 

 application of a warm moisture, they come forth from the 

 shell strong and vigorous ; but, -^ intelligent of seasons," 

 they begin instinctively to seek hybernating quarters at a 

 moist season of the year, and before the cold has benumbed 

 their powers ; and, if roused ultimately, their languid move- 

 ments evidence their weakness, and bespeak our sympathy to 

 leave them to repose. Whether the vital functions in these 

 creatures are similarly aff*ected 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 pulmoniferous 

 freshwater MoUusca, pass the winter in a state of hybernation. 

 I believe that the naked slugs do not hybernate ; for, although 

 they retire under stones, clods of earth, or moss, to protect 



* " This living principle has the singular property of remaining dormant 

 and inert for years or ages ; without, therefore, ceasing to exist. We all 

 know that seeds may be kept a long while unsown, and yet grow whenever 

 planted in a suitable soil . This, again, is like animals which have been 

 found enclosed in trees, and yet have revived. When plants are buried in 

 the ground to a greater depth than is natural to them for their proper 

 growth, they do not vegetate; but they do not therefore die; they retain 

 their power of vegetation to an unlimited period; and when, by any acci- 

 dent, brought so near the surface as to suit their evolution, they begin 

 immediately to grow." (Turner's Sacred History^ p. 195.) 



