their Respiration, 117 



themselves from the cold and storms of the season, yet I have 

 always found them immediately to resume their activity when 

 taken from their concealments, 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. 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 BMimus Kdmbeul appa- 

 rently passes the nxiinter^ or dry season, in a deep slumber, like 

 the snails ofT^urope ; 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 themselves 

 against the long droughts which continue for eight or nine 

 months uninterruptedly. [Hist. Nat. dn Senegal, p. 18.) 



None of the hybernating Mollusca exhibit any remarkable 

 cunning in the selection of their hybernacula or winter quar- 

 ters. On the approach of the cold weather, the terrestrial 

 tribes 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 50th degree of Fahrenheit, cold-blooded animals 

 begin their winter slumber, and, previously prepared by that 

 instinct 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 

 deathlike 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. 



M. Gaspard has given a minute and' a very interesting 



* " The marine Mollusca probably migrate in part from the shallower 

 to the deeper waters in cold winters : many, however, hybernate." {^Duncan 



I 3 



