10 



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 the 

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

 mant state. Probably they will arrive at maturity by July or August 

 next. The sixth specimen did not bury itself until the 15th of 



August. 



Second Experiment with Helix aspersa. 



A pair of Helix aspersa having been procured in the act of copu- 

 lation on the 19th of May 1852, they were placed in confinement. 

 Each individual deposited about 70 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 themselves (with their heads 

 downwards as with Helix pomatia, 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 July the 18th, when they were almost fully grown. 

 It is worthy of remark that this species, as well as Helix pomatia 

 and Helix nemoralis, and probably other of the Helicse, form an oper- 

 culum at the aperture, after which they retire considerably within 

 the shell, and form a second (much thinner), behind which they 

 rest during the winter. 



It would be swelling this paper too much to describe all the obser- 

 vations in full ; it will perhaps therefore be considered sufficient to 

 remark that the process of growth within the ground takes place 

 with Helix nemoralis, Helix virgata, Helix caperata, and Helix hispida. 

 Helix rotundata burrows into decayed wood to increase the size 

 of its shell. Zonites radiatulus appears to remain on decaying blades 

 of grass ; whilst Pupa umbilicata, Clausilia nigricans and Bulimus 

 obscurus bury their heads only to increase their shells. With respect 



