Physiology of Helix Pomatia. 95 



sides toward the lowest part, and the result is a deformed and in- 

 sufficient operculum. 



Finally, I believe I have established that the membranous par- 

 titions are more numerous at the end than at the beginning of win- 

 ter, and in the snails inhabiting the mountains, than in those found 

 on low ground. 



§ 3. The snail thus enclosed passes six months in a state of total 

 torpidity, and it is not until the spring that it bursts its prison and 

 returns to its ordinary habits. But if we take off the opercu- 

 lum shortly after its formation, it emerges from its shell, walks 

 about again, and assumes different habits according to circum- 

 stances. 1st. If the temperature be about 12 or 15 degrees 

 Reaum. (59-67° Fahr.) and the snail finds food, it begins to feed 

 again, recovers the whiteness of its mantle, which had become 

 grey and lean, and in about eight days makes another form, in 

 which it buries itself, and forms a fresh operculum, as solid as the 

 former. 2dly. If the temperature should be colder, as for In- 

 stance, 8 or 10' R. (50-55° F.) it eats but very little, and soon 

 forms its hole in the earth, but produces only a slight, flexible, 

 greyish, operculum, with but little earthy matter in its composi- 

 tion. 3dly. If the temperature be but little above the freezing 

 point, as at 3 to 6° R. (39-45° F.) it refuses food entirely, scarcely 

 moves, has no strength to make its .form, and produces only a 

 membranous enclosure. 4thly. If the temperature be below freez- 

 ing point, the snail makes no attempt at hibernation, and soon pe- 

 rishes with cold. 



% 4. It appears from the analyses to which I have submitted the 

 operculum, that it consists wholly of carbonate of lime. Thus 

 it dissolves rapidly with a brisk effervescence in the mineral 

 acids and in vinegar ; and all these solutions, treated with soda or 

 potass, throw down an abundant white precipitate. On the other 

 hand, calcination reduced it to the state of caustic lime. 



The secretory organ of this calcareous matter is the collar or 

 finger of the mantle, a most important organ, since it is also the 

 part from which the shell itself is formed.* It is found to contain 

 * Although it would appear from some circumstances, such as the filling up 

 of the apex of the shell, that other parts are occasionally capable of producing 

 a calcareous secretion, yet there is no doubt that the edge or collar of the man- 



