102 Insect Life : Its Why and Wherefore 
a shell, though a thin and delicate one, 
which is hidden beneath an outer covering of 
skin. If the raised part or “ mantle ” of 
the slug is carefully removed with a fine, 
sharp knife, the shell will be found beneath, 
quite rudimentary, it is true, when com- 
pared to that of the snail, but still it can 
be removed and dried for purposes of exam- 
ination. The body of the slug, elongated 
in shape, carries a distinct head with four 
tentacles, the upper pair of which carry the 
eyes. Both the tentacles and the head are 
provided with muscles which enable them 
to be withdrawn quickly, and when alarmed 
the animal will withdraw these beneath 
its “ mantle.” The creeping disc extends 
the whole length of the animal and acts 
as the surface of the foot, secreting a 
slimy mucus which helps greatly its means 
of locomotion. On wet evenings, or after 
rain has fallen, these creatures are found 
in much larger numbers, as the moisture 
on the surface of the ground makes it 
easier for them to travel. Although the 
slug is possessed of eyes it would seem 
to be more sensitive to the slightest touch 
than the brightest light. I have gone 
