LAND SNAILS. 95 
at were, that the shells of the Helicide increase 
but little for a considerable period, never arriving 
at maturity before the animal has once become 
dormant. The shells do not grow whilst the 
animal itself remains dormant, and the growth 
is very rapid when it does take place. Most 
species bury themselves in the ground to in- 
crease the dimensions of the shells. In illus- 
tration follows here one of his experiments :— 
“A pair of Helix aspersa had deposited their eggs, 
which began to hatch on the 20th of June; 
these 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 them- 
selves with their heads downwards (in winter 
they and other species buried themselves with 
the head upwards), appearing again in a week 
double the size. This process was carried on at 
about fortnightly intervals until the 18th of July, 
when they were almost fully grown. 
“The process of growth within the ground 
takes place with Helix nemoralis, H. virgata, and 
H. hispida. But H.rotundataburrows into decayed 
wood to increase the size of its shell; whilst 
Helicella radiatula appears to remain on decaying 
blades of grass; and Pupa wmbilicata, Clausilia 
rugosa, and Bulimus obscurus bury their heads 
