GASTEROPODA. 



177 



size. They form in some countries, as Switzerland, Brit- 

 tany, and some parts of Germany, a considerable article 

 of commerce, and are fed by thousands in places made 

 on purpose for them. It is supposed the Romans also 

 fattened the Helix pomatia in the same manner ; even at 

 the present day the Helix aspersa is sold in Covent Garden 

 market, to be used, boiled in milk, for diseases of the 

 lungs. They are also sent to America from this country 

 as a delicacy. 



These animals become torpid about October (at least in 

 England), and remain so during the winter, having first 

 closed the aperture of their shells with an epiphragma which 

 they throw off, and emerge when warm weather returns ; 

 some of them form two or three of these doors, one within 

 the other, so as completely to exclude the cold, and others 

 bury themselves in the earth. The Helix aspersa, which 

 is the pest of our gardens, is more influenced by the 

 weather than many of the smaller sort; for upon the 

 first appearance of cold these molluscs creep into crevices 

 and under stones, clustering and clinging together as if 

 they were capable of communicating warmth by associa- 

 tion. In the centre of the epiphragma is an exceedingly 

 minute orifice, communicating with the lungs; and this 

 minute hole, though not large enough to admit a drop of 

 water, is of sufficient capacity for the passage of air for 

 the purpose of extremely slow, but not totally extinct 

 respiration.* 



Many instances have been known of the great tenacity 

 of life which snails possess. A gentleman received some 

 species closely packed with marine shells from the Mau- 

 ritius ; the day after they were unpacked they were dis- 

 covered wandering about, apparently uninjured from their 



* Gray's edition of Turton's Manual. 



