GEOWTH OF SHELLS. 5 



siderable period, never arriving at maturity before 

 the animal has once become dormant. The shells, 

 it would appear, do not grow whilst the animal itself 

 remains dormant, but the growth is very rapid when 

 it does take place. Most species bury themselves 

 in the ground to increase the dimensions of the 

 shells ; and in illustration of this Mr. Lowe states 

 that a pair of Helix aspey'sa had deposited their 

 eggs, which began to hatch on the 20th of June. 

 The young ones grew but little during the summer : 

 they buried themselves in the soil on the 10th of 

 October, coming again to the surface on the 5th of 

 April, not having grown during the winter. In 

 May they buried themselves with their heads down- 

 wards (in winter they and other species buried 

 themselves with the heads upwards) appearing again 

 in' a week, double the size. This process was car- 

 ried on at intervals of about a fortnight until the 

 18th of July, when they were almost fully grown. 



The process of growth within the ground takes 

 place with Helix neinoralis, H. virgata, and H. his- 

 pida. But H. rotundata burrows into decayed wood 

 to increase the size of the shell : whilst Zonites 

 radiatulus appears to remain on decaying blades of 



