30 Our British Snails 



organisms on which I feed. I can thus travel 

 fifteen feet a day, or about a mile in a year. 



"I have no eyes, but distinguish well between 

 light and shade by means of the surface of my 

 body when exposed. I breathe, that is, get oxygen 

 from the water, by means of gill-plates. As 

 regards other internal organs, I differ not much 

 from H. aspersa, but I am either male or female. 

 Outside I am black and uncomely ; but within 

 I am pearly- white, and but for my power of 

 forming pearls round an irritating grain of sand 

 the civilization of England would have come 

 to pass later than it did, for it was the report 

 of my pearls which brought Caesar to Britain." 



Now let us enumerate the species of land and 

 freshwater shells to be found, (all but two) in 

 England, and most of them in Ireland or Scotland. 



Arioji ater is a large (3 to 5 inches) and common 

 slug, usually black (whence its name ater), but 

 also red, brown, or white. In some varieties 

 the foot-fringe is orange. When irritated it 

 contracts into a hemispherical lump. A fev/ 

 chalky granules under the mantle are the repre- 

 sentatives of a shell. See the illustration of three 

 specimens on p. 31. That hole in the mantle is the 

 breathing orifice, and its forward position is a 

 characteristic of the group Arion. The body of 

 slugs is kept moist by a constant exuding of slime 

 from a gland in the tail. 



