x MOLLUSC A 131 



aided by an acid secretion, for in such situations the 

 recently exuded slime from the foot shows an acid reaction 

 with litmus. 



Land snails are all hermaphrodite. H. aspersa 



e ?ion UC " ^ a y s fr m 40 to 100 eggs at a time, in a hole 



in moist earth. They are round transparent 



objects about -J- inch in diameter. The common garden 



snail is full grown when a year old, but it lives four or 



five years. 



Other Common Species of the Genus Helix. 



Helix hortensis (the White-lipped Snail). A rather smaller 

 species than H. aspersa, with distinct darker spiral bands 

 of colour on the shell, not crossed by transverse white bands. 

 The shell is 1 inch across, and it has 5 J whorls ; the lip is 

 white. 



Helix nemoralis (the Grove Snail or Brown-lipped Snail). 

 The shell is 1 inch across, very varied in colour, often clear 

 yellow, with one to five spiral dark bands running round 

 it ; the lip of the shell is reflected and usually brown ; there 

 is no umbilicus; the body is brown tinged with yellow; very 

 like H. hortensis except for the brown lip. This snail is very 

 common in hedges, and is often 

 found feeding on stinging nettles. 



Helix pomatia (Apple or Roman 

 Snail). This is a large snail 

 common in calcareous districts. 

 The shell is If inch across, and 

 is thick, strong, yellowish, or 

 pinkish -white, with spiral light- 

 brown bands ; the outer lip of the 

 shell is thickened ; the umbilicus 

 is small but distinct (Fig. 85). A 

 peculiarly solid calcareous epi- 

 phragm is secreted by the mantle 

 before the winter, and may be mella"c "and Umbilicus "u." 

 found discarded on the ground 



in spring. Before hibernating, each snail excavates with its 

 foot a hole, which it roofs in and lines with earth and dead 

 leaves, making with its slimy mucus a kind of mortar, which 



