40 GROWTH OF THE SHELL chap. 



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

 conducted ^ 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 

 the dimensions of their shells. 



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

 regularly fed on lettuce and cabbage leaves 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 H. hispida. 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 doivnwards^ in the 

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

 grown so rapidly as to be equal in size to H. piscina. 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 the winter and they became 

 dormant. 



A similar experiment, with similar results, was carried on 

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

 the summer they grew but little, buried themselves on 10th 

 October with the head upwards^ and rose to the surface again on 

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

 buried themselves with the head doiumvards, and appeared 

 again in a week double the size ; this went on at about fort- 

 nightly intervals until 18th July, when they were almost fully 

 grown. 



Helix nemoralis, H. virgata^ H. caperata^ and H. hispida bury 



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



