UNIVALVES. 163 
seconds the horns reappear; the eyes run up the 
narrow transparent channel, down which they had 
descended, and the Helix journeys on its way. 
Now the reason of such a peculiar construction is 
obvious. The snail is thus enabled to command a 
' more extensive sphere of vision, than if the eyes were 
situated in the head. Moreover, the pliability of 
the antennze enables them to turn in different direc- 
tions, while the ease with which they are capable of 
being extended, or contracted, like a pocket telescope, 
admits of the ready withdrawing of the head into the 
shell; an arrangement which beautifully harmonizes 
with the extreme weakness of the animal. 
Shakspeare 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 remark- 
ably slow. How shall we account for this extra- 
ordinary fact, since the snail is light, and small, and 
apparently by no means incapable of comparatively 
rapid motion? Probably by the viscous nature of 
its juices, which are extremely tardy in their circula- 
tion, and consequently produce a considerable degree 
of sluggishness in the movements of the animal. 
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