TORPIDITY OF REFTILES. 139 



times happens that during intense frosts, accom- 

 panied by a piercing east wind, thousands of 

 eels, though buried in the mud, have been 

 destroyed ; crawling from their holes in the 

 agonies of death, they have been washed down 

 the stream to the tideway, and thrown upon 

 the beach. Many instances of this kind are on 

 record. In the Arctic regions there are no 

 eels ; none inhabit the rivers of Siberia, the 

 Wblga, the Danube, or any of its tributary 

 streams. Few or no eels exist in the mountain 

 streams of the northern portion of our island. 



From the vertebrate animals, let us turn to 

 the invertebrate. All our terrestrial mollusca, 

 or snails, and slugs, hybernate. They retire to 

 concealed nooks and crevices, or into the earth, 

 under flagstones, into deep cellars or vaults, 

 and there become torpid. The shelled snails, 

 having fixed upon a convenient retreat, gra- 

 dually retire within their shell, spreading over 

 the orifice repeated layers of mucus, which 

 harden into a firm tissue, bearing no unapt 

 resemblance to a drum-head in miniature. The 

 common garden snail, (Helix aspersa,) before 

 closing the mouth of its shell with a membranous 

 operculum (lid,) glues it by means of mucus to 

 the surface of some object, as a portion of wooden 

 paling, the inside of a garden-pot, the under 

 surface of a bench, or garden seat, etc. ; thus 

 secured, it continues till spring, when the oper- 

 culum is forced away, the shell disengaged, and 

 the animal's self-liberation effected. 



M. Gaspard has detailed some curious cir- 



