762 MOLLUSCA — GONCHIFERA. 



As the snail is furnished with all the organs of life and sensation, it is not 

 wonderful to see it very voracious. It chiefly subsists upon the leaves of 

 plants and trees, but is very delicate in its choice. At the approach of 

 winter, it buries itself in the earth, or retires to some hole to continue in a 

 torpid state, during the severity of the season. It is sometimes seen alone ; 

 bnt more frequently in company in its retreat ; several being usually found 

 together, apparently deprived of life and sensation. For the purpose of con- 

 tinuing in greater warmth and security, the snail forms a cover or lid to the 

 mouth of its shell with its slime, which stops it up entirely, and thus pro- 

 tects it from every external danger. When the cover is formed too thick, the 

 snail then breaks a little hole in it, to correct the effect of that closeness, 

 which proceeded from too much caution. In this manner, sheltered in its 

 hole from the weather, defended in its shell by a cover, it sleeps during the 

 winter ; and for six or seven months, continues without food or motion, 

 until the genial call of spring breaks its slumber, and excites its activity. 



The snail, having slept for so long a season, awakes in one of the first 

 fine days of April, breaks open its cell, and sallies forth to seek for nourish- 

 ment. At first, it is not very difl[icult in the choice of its food; almost any 

 vegetable that is green seems welcome ; but the succulent plants of the 

 garden are chiefly grateful ; and the various kinds of pulse are, at some 

 seasons, almost wholly destroyed by their numbers. A wet season is 

 generally favorable to their production ; for this animal cannot bear very dry 

 seasons, or dry places, as they cause too great a consumption of its slime, 

 without plenty of which it cannot subsist in health and vigor. 



CLASS II. — CONCHIFERA.i 



Animal soft, inarticulaled, destitute of head or eyes, and alivays fixed in a valve 

 sheU ; bronchia external ; circulation simple ; heart unilocular. 



The animals of this class have no apparent head ; and their mouth con- 

 cealed under the mantle, or at the junction of its two lobes, and destitute of 

 jaws or hard parts, appears to be as the orifice of a short oesophagus. The 

 mantle or cloak which envelopes the body is large, in two lobes, and incloses 

 the trunk, like the cover of c book. In some families, however, this mantle 

 is united before, and then forms a tubular covering, open at both ends. 

 The mantle, besides, often forms two tubes or syphons, of which one con- 

 ducts the water to the bronchise, and the other serves as a canal for dejec- 

 tions. This mantle is always furnished with a shell of two valves, uniter' 

 by a hinge or ligament; and strong transverse muscles, attached to the 



(' Mollusca acephala, Cuv.) 



