176 INTRODUCTION TO CONCHOLOGY. 



which the eyes are situated, appearing like small dark spots, 

 sparkling and orbicular. These, on the approach of danger, 

 are rapidly inverted into the head, which immediately dis- 

 appears beneath the shell. In the course of a few seconds 

 the horns appear, the eyes run up the narrow transparent 

 channel down which they had descended, and the Helix 

 journeys on its way. 



IN'ow the reason for such a peculiar construction is ob- 

 vious. The snail is thus enabled to command a more 

 extensive sphere of vision than if the eyes were situated in 

 the head. Moreover, the pliabihty of the tentacles enables 

 them to turn in different directions, while the ease with 

 which they are capable of being extended or contracted, 

 admits the ready withdrawing of the head i]ito the shell ; 

 an arrangement which beautifully harmonizes with the 

 extreme weakness of the animal. 



Shakespeare notices this striking peculiarity. "I can 

 tell,"' said the faithful adviser of King Lear, " why a snail 

 has a house." " Why ? " replied his unfortunate master. 

 " Why, to put his head in ; not to give it away to his 

 daughters, and to leave his horns without a case.""* 



The movements of the common Helix are remarkably 

 slow. But how shall we account for this extraordinary 



