GASTEROPODA. 233 



storms that are howling over its head, without sensa- 

 tion, circulation, respiration, or any of the ordinary 

 functions of life. When the twittering Swallows ar- 

 rive from their long migrations, and the voice of the 

 Cuckoo begins to be heard in the leafing woods, the 

 buried Snail feels the reviving influence of spring, and 

 heaves up his head. The manner in which its es- 

 cape is effected is simple, and easily comprehended. 

 The air which is contained in the cells is again in- 

 spired by the animal, and the membranous parti- 

 tions burst one by one, by the projection of the foot 

 through the mantle. When it arrives at the thick 

 and strong operculum, the Snail, making a last ef- 

 fort, bursts and detaches its most obtuse angle. 

 Then, insinuating by degrees the edge of the foot 

 between it and the shell, it at length forces it off, 

 bursts its habitation, and crawls forth to satiate its 

 returning appetite with the leaves and flowers of 

 spring. 



It appears that moisture as well as warmth is ne- 

 cessary to the activity of Snails ; and that, during the 

 heat of summer, they retire within their shells, clos- 

 ing the aperture with a membrane of dried slime. 

 In this state they remain night and day while the 

 weather continues dry ; but on the occurrence of a 

 shower they again crawl about, which they may 

 also be induced to do by watering the ground around 

 them. 



We have seen that it is the edge or collar of 

 the mantle which secretes the shelly operculum ; it 

 is the same organ which ordinarily forms and en- 



