SLUGS AND SNAILS. 



271 



the slime is also yellowish. The shell consists of a number of 

 small separate calcareous grains. This species is a scavenger as 

 well as being injurious. 



Another curious group of Slugs 

 belong to the genus Testacella. 

 These molluscs (fig. 142), of which 

 there are three species in England, 

 feed almost entirely on earthworms. 

 The TestacellsB are the only true 

 predaceous land mollusca. They 

 hunt the earthworms in their bur 

 rows, and devour huge lobworms 

 much larger than themselves. The 

 mouth is furnished with long curved 

 teeth (t), so as to hold the victim. 

 They live for four or five years. 



The eggs are laid separately, and «^^'»d"ia ; w, worm ; t, teeth from 

 resemble hen's eggs in shape, and 

 have a very thick skin. Only six or seven ova are laid, 



Fig. 142. — Testacella. 

 Testacella hdliotidea : b, head ; 



Snails (Hblioid*). 



The SnaUs, like Slugs, are nocturnal and crepuscular, seldom 

 crawling about in the daytime, unless after heavy rains. The 

 latter habit has given rise to a popular idea that snails come in 

 rain-clouds. When the breeding season is on, the male organs 

 are supplemented by one or more curious crystalline darts, which 

 they thrust out at one another : these curious structures, found 

 in special sacs called " dart-sacs,'' are peculiar to the genus Hdix. 

 The eggs are laid in batches in slanting galleries underground 

 formed by the " mother '' snail : they are white, round, semi- 

 transparent bodies. 



The following snails have been brought to the author's notice 

 as being very injurious : The Garden Snail {Helix aspersa), the 

 Wood Snail {H. nemoralis), the Strawberry Snail {H. rufescens), 



