40 GROWTH OF THE SHELL chap. 



Growth of the Shell. — Mr. E. J. Lowe, many years ago, con- 

 ducted^ some interesting experiments on the growth of snails. 

 The facts arrived at were — 



(1) The shells of Helicidae increase but little for a consider- 

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

 become dormant. 



(2) Shells do not grow whilst the animal itself remains 

 dormant. 



(3) The growth of shells is very rapid when it does take 

 place. 



(4) Most species bury themselves in the ground to increase 

 tiie dimensions of their shells. 



Six recently hatched IT. pomatia were placed in a box and 

 regularly fed on lettuce and cabbage lea\'es from August until 

 December, when they buried themselves in the soil for winter ; 

 at this period they had gradually increased in dimensions to the 

 size of M. hisjnda. On the 1st April following, the box was 

 placed in the garden, and on the 3rd the Helices reappeared on 

 the surface, being no larger in size than they were in December. 

 Although regularly fed up to 20th June, they were not per- 

 ceptibly larger, but on that day five of them disappeared, having 

 buried themselves, with the mouth of the shell doivmvards, in the 

 soil. After ten days they reappeared, having in that short time 

 grown so rapidly as to be equal in size to IT. pisana. On the 

 15th July they again buried themselves, and reappeared on 1st 

 August, having again increased in size. For three months from 

 this date they did not become perceptibly larger; on 2nd 

 November food was withheld for tlie winter and they became 

 dormant. 



A similar experiment, with similar results, was carried on 

 with a number of H. aspersa, hatched on 20th June. During 

 the summer they grew but little, bm^ied themselves on 10th 

 October with the head to2nvards, and rose to the sm-face again on 

 5 th April, not having grown during the winter. In May they 

 buried themselves with the head dowmuards, and appeared again 

 in a week double the size ; this went on at about fortnightly 

 intervals until 18 th July, when they were almost fully 

 grown. 



Helix nemoralis, H. virgata, H. caperata, and H. hispida bmy 



^ Phil. Trans. 1854 (1856), p. 8. 



