LUNG-BREATHING GASTROPODS 433 



Thus completely shut off from the outer world and protected against 

 enemies and excessive evaporation (see Section B), the snail reposes 

 until returning spring puts an end to the cold and scarcity of food. 

 The animal now throws off the lid from the opening of its dwelling and 

 reawakens to a new life. 



6. It is only when it appears in large numbers that the vineyard 

 snail commits any appreciable damage. In South Germany, Austria 

 and the countries of Southern Europe, it is got rid of by a very simple 

 and expeditious method, forming (in common with several other large 

 species) a favourite article of consumption for fast-days. 



D. Reproduction. 



If a vineyard snail is discovered in the summer with only the upper 

 portion of its shell projecting from the soil, it is a sure sign that we have 

 caught it in the act of depositing its eggs. If it be lifted off the ground, 

 we shall find that it has dug, by the help of its foot, a pit, often as much 

 as 4 inches deep, in which it deposits thirty, forty or more white- 

 coloured eggs about the size of a pea. These eggs are protected from 

 injury by a parchment-like membrane impregnated with lime salts (see, 

 however, freshwater snails), and prevented from drying up by the damp- 

 ness of the soil. After the deposition of the eggs the female refills the 

 pit, and if we examine it a few weeks later we shall already find the 

 delicate transparent young. 



Other Land Snails. 



The shells of the various snail species living on land, like the vineyard 

 snail, vary considerably in form and colour. In addition to these, how- 

 ever, we meet with some which retain only a minute rudiment of a shell 

 within the mantle, which forms a shield-like structure covering the dorsal 

 surface (naked gastropods, or slugs). 



Examples of this group are the Road Slug (Arion empiricorum) , 

 which is frequently met with in woods and among bushes. It may 

 attain to a length of 6 inches, and varies in colour from orange to black. 



Another common species, the Garden Slug (Limax agrestis), fre- 

 quently does much damage to crops and vegetables (strawberries). 



A large number of pulmonate snails also live in fresh water, especially 

 in calm ponds and pools. Their greenish-brown shells, which resemble 

 the colour of the bottom and of aquatic plants, are accordingly much 

 more delicate than those of most land snails. The same also applies to 

 the bodies of the animals, and even to their eggs, which are enveloped in 

 mucus (spawn, see common frog), and are glued to leaves and stones in 

 sausage-like balls. In these snails the eyes are not placed on peduncles, 

 and they possess only one pair of feelers, which are not introvertible. 



