280 FUNCTIONS AND INSTINCTS. 



the young of quadrupeds ; the yolk of the egg to 

 those of birds, tortoises, and lizards; and the 

 white of the egg to frogs and toads, has made 

 this pellicle or coat the best nutriment of the 

 young snail. In fact, this pellicle, consisting of 

 carbonate of lime, united to animal substance, is 

 necessary to produce the calcareous secretion of 

 the mantle, and to consolidate the shell, as yet too 

 soft for exposure. When this envelope is eaten, 

 the little snail finds its nutriment, more or less, 

 in the vegetable soil around it, and from which 

 it continues to derive materials for the growth 

 and consolidation of the shell. It remains thus 

 concealed for more than a month, when it first 

 issues forth into the world, and without respect 

 of persons, attacks the vegetable productions 

 around, returning often to an earthly aliment, 

 probably still necessary, for the due growth and 

 hardening of its portable house. These snails 

 cease feeding when the first chills of autumn are 

 felt, and associating, in considerable numbers, on 

 hillocks, the banks of ditches, or in thickets and 

 hedges, set about their preparations for their 

 winter retreat. They first expel the contents of 

 their intestines, and then concealing themselves 

 under moss, grass, or dead leaves, each forms, 

 by means of its foot, and the viscid mucus which 

 it secretes, a cavity large enough to contain its 

 shell. The mode in which it effects this is re- 

 markable ; collecting a considerable quantity of 



