174^ INTRODUCTION TO CONCHOLOGY. 



the works of nature, an original contrivance. ^^ Other 

 animals have their proper retreats, their hybernacula also, 

 or winter quarters, but the snail carries these about with 

 him. He travels with his tent ; and this tent, though 

 necessarily both hght and thin, is completely impervious 

 either to moisture or to air.'" The young Heliv, like his 

 numerous brethren of the univalve order, emerges into 

 life with a covering adapted to his exigencies, which en- 

 larges with his growth by means of a certain viscous exu- 

 dation from innumerable pores. Now the aptness of this 

 secretion to the purpose for which it is designed, its property 

 of congealing into a firm and hard substance, independent 

 of any effort on the part of the inhabitant, cannot be re- 

 ferred, as the same admirable writer has justly observed, 

 to any other cause than express design ; and that not on 

 the part of the unconscious artist, who, although he might 

 build the house, could not supply the materials. Moreover, 

 the form of the building, with its pillar and convolution, 

 is not only a very artificial one, but admirably adapted to 

 the exigencies of the inhabitant ; which is confessedly one 

 of the most feeble and unprovided of all artificers. Nay 

 more, the testaceous coverings of such as live on land, or 

 inhabit still ponds and ditches, are scarcely able to resist 



