HYBERNATION. 263 



None of the hybernating mollusca exhibit any remark- 

 able cunning in the selection of their hybernacula, or winter 

 quarters. On the approach of the cold weather the terres- 

 trial tribes dig into the ground or seek out a convenient 

 station in crevices of old walls, at the roots of coarse grass, 

 or in tufts of moss, and, retiring within the shell, they close 

 up its aperture by a membranous or calcareous epiphragm, 

 which serves, at the same time, to fix or cement the shell 

 to the wall or body against which it rests. * At the same 

 period the aquatic tribes descend to the bottom of their 

 ponds and ditches, sink a little in the soft mud, and cover 

 over the mouth of the shell with a transparent gelatine. 

 In general when the temperature of the air sinks below the 

 fiftieth degree of Fahrenheit, cold-blooded animals begin 

 their winter slumber, and, previously prepared by that in- 

 stinct which operates as wisely as if right reason had fore- 

 seen the coming evil, they gradually, with the increasing 

 cold, sink into a state which resembles more the stillness of 

 death than the quietness of sleep ; a state without motion, 

 or feeling, or sense, or heat, and in which the heart and 

 lungs, the vital organs, perform their functions more and more 

 feebly, until they also rest still in the general quiescence ; 

 and in this death -like condition these animals continue " for 

 five, six, seven, or even eight or nine months, according to 

 the climate and season," until the genial warmth and dews 

 of spring recall them anew to life and action, -j- 



M. Gaspard has given a minute and a very interesting 

 account of the hybernation of Helix pomatia in the first 

 volume of the " Zoological Journal," to which I must refer 

 you for the particulars. This species forms, by aid of its 

 foot and a very glutinous secretion, an excavation, or nest, 

 in which it buries the shell, and it then closes the aperture 

 with a thick calcareous epiphragm, and with several interior 

 membranous partitions, which are more numerous at the 

 end than at the beginning of winter, and in the snails in- 

 habiting the mountains than in those found on low ground. 

 Thus buried and enclosed it passes six months in a state 



vations on the torpidity of the Bulimi, by Mr. Reeve, in Ann. and Mag. N. 

 Hist. ser. 2, i. 272. 



* " It is composed of a viscous slabber, from the body of the animal 

 which condenses into a kind of toughish coriaceous, or leatbcr-like, sub- 

 stance, and is pretty thick. This lid, or crust, is never attached to the body 

 of the animal, as in the sea- univalves, but merely covers tlie mouth ; nor is it 

 ever wrought with a spiral or with concentric circles, or indeed any other 

 regular work." — Da Costa, FJcm. Cunc/ioloiii/, p. 121. 



t Helix naticoides passes ten months of tin' year in this state, buried 

 to the depth of twenty centimetres in the earth." — I n;ap. Mullusy. ]>. 93. 



