304 THE BRITISH NATURE BOOK 



As is well known, snails can extend a large part of their bodies outside their 

 shells at will ; to see the under part in action, place a snail on a sheet of glass, 



and look through it as the snail moves. 

 Notice, first of all, the head, which 

 has a very business-like mouth and 

 lips ; on the top are the " horns " in 

 reality two pairs of tentacles, the 

 back and larger pair carrying at their 

 tips a black spot, which is the eye. 

 Side view of a living Snail, as an example of The other pair are sensitive organs of 



the division of Mollusca called Gasteropoda : f, touch, and possibly of Smell as Well. 



foot-the dotted line shows the upper limit of These tentacles are easily with- 



the muscular portion ; m, mantle ; o, opening - . , , . 



between mantle and body ; s, shell. drawn into the body, and the action 



is very curious. If you tied a string 



to the tip of one of the fingers of a glove, on the inside, and pulled, you would 

 produce the same movement which in the snail's anatomy is produced by a 

 muscle running up the hollow tentacle and fastened to the summit. 



The ventral part of the snail is known as the " foot " and has powerful 

 muscles, which may be seen in rippling movement on the glass. The part 

 of the body which supports the shell is known as the " collar," and is cream 

 coloured. In its right side may be seen a large hole opening and closing in a 

 rhythmic manner. This is the breathing organ and leads to the lung cavity. 



The slime which a snail leaves behind it comes chiefly from a special opening 

 just under the mouth, but it is also continually exuding from the whole of the 

 skin. 



But as the snail feeds it leaves behind it very frequently another track, 

 made by the rasping tongue or radula. Most snails are vegetable feeders, 

 although some slugs are carnivorous. Testacella, for instance, devours earth- 

 worms. But in all cases the food is eaten by means of the remarkable rasp, 

 a horny ribbon covered with thousands of teeth, set backwards, the whole 

 worked to and fro against its hard horny upper jaw. This can be beautifully 

 seen in water snails, if kept in an aquarium, when they browse upon the green 

 algae growing on the glass. Similar rasps are found in the sea " snails " or 

 univalves. In the Garden Snail the tongue has 135 rows of 105 teeth 14,175 

 in all. Small wonder that it can do such damage ! 



All snails are hermaphrodite that is, have both male and female organs, 

 but the eggs are not fertilized except by mating. Before that act the snail 

 discharges a remarkable dagger or spear-shaped dart of chalky substance 

 into the body of its companion. That of the Garden Snail is exactly like a 

 poniard, handle and all, and as the forms vary in different species, these darts 

 form means of identification. 



The eggs are laid in batches of thirty or more, deposited in moist places, 

 each egg being in a round leathery shell, and hatching in about a month. 



In winter the snail retires to some sheltered spot, or buries itself in the earth, 



