500 Royal Society. 



been kept in confinement since the day it was hatched. Each 

 species has been placed in a separate box (filled with soil to the 

 depth of three inches), and care has been taken to feed the Mollusca 

 every other day, the food chiefly consisting of the leaves of the 

 lettuce and cabbage. In very dry weather the soil has been moistened 

 with rain-water about once a week ; in the box containing Helix: 

 pomatia small lumps of chalk have been mixed with the soil. 

 The species experimented upon were : — 



Helix aspersa 



— caperata 



— hispida 



— nemoralis 



— pomatia 



— rotundata 



— virgata 



Zonites cellarius 



— lucidus 



— nitidulus 



— radiatulus 

 Bulimus obscurus 

 Clausilia nigricans 

 Pupa umbilicata 



The facts arrived at are, — 



1st. The shells of Helicidse increase but little for a considerable 

 period, never arriving at maturity before the animal has once become 

 dormant. 



2nd. Shells do not grow whilst the animal itself remains dor- 

 mant. 



3rd. The growth of shells is very rapid when it does take place. 



4th. Most species bury themselves in the ground to increase the 

 dimensions of their shells. 



First Experiment with Helix pomatia. 



A specimen of this species having deposited thirteen eggs which 

 were hatched during the first week of August 1852, six of the 

 young ones were deposited in a box (having a lace cover) placed 

 in the shade. The young Helices were regularly fed every other 

 day until the beginning of December, when they buried themselves 

 in the soil for winter ; up to this period they had gradually increased 

 in dimensions to the size of Helix hispida. From December until 

 April the soil was kept dry, the box being placed in the cellar. On 

 the 1st of April they were replaced in the garden, the soil having 

 previously been copiously watered. On the 3rd of April the young 

 ones appeared on the surface, being no larger in size than they were 

 in December, and although regularly fed up to the 20th of June 

 they scarcely increased, not being perceptibly-larger in size than 

 they were in December. However, on the 20th of June five of 

 them disappeared, having buried themselves (with the mouth of the 

 shell downwards) in the soil ; on the 30th of June they reappeared, 

 having in ten days grown so rapidly as at this time to become equal 

 in size to Helix pisana. They again buried themselves on the 15th 

 of July and reappeared on the 1st of August, having again in- 

 creased in size. From this date they did not apparently become any 

 larger, and on the 2nd of November food was withheld for tlie 

 winter, and at the present time (February 14th) they are in a dor- 



