SNAILS AND SLUGS 
171 
the herbage in our neighbour’s garden. If, 
however, we were to stop and examine one of 
these creatures more closely, we should find 
that it exhibited many interesting features. 
Its head, for instance, is furnished with two 
pairs of tentacles or “ horns,” the eyes being 
situated upon the extremities of the hindermost 
and longer ones. The greater part of its body 
is permanently enclosed within the shell, but 
when the animal is progressing it protrudes an 
organ known as the “ foot,” which tapers 
behind and is furnished with a mucous gland 
that secretes the slimy trail that marks its 
passage as it crawls along. 
All snails are provided with a so-called 
“ tongue ” or lingual ribbon that is fixed to the 
floor of the mouth, the under surface or “radula ” 
being covered with a multitude of small and 
pointed tooth-like excrescences that are coated 
with a hard substance called chitin. These 
teeth, which are arranged in a series of rows and 
are capable of being erected at the will of the 
owner, vary considerably in number in the 
different species of the snail family, the common 
garden-snail possessing about one thousand five 
hundred, while the great black slug has as many 
as thirty thousand. 
When feeding, the animals pass their tongues 
backwards and forwards over their food, the 
