HABITS AND ECONOMY OP THE MOLLUSCA. 19 



years, although in the warm climate of Calcutta. The eyclosto- 

 mas, which are also operculated, are well known to survive impri- 

 sonments of many months ; but in the ordinary land-snails such 

 cases are more remarkable. Some of the large tropical bulimia 

 brought by Lieutenant Graves from Valparaiso, revived after being 

 packed, some for thirteen, others for twenty months. In 1849, 

 Mr. Pickering received from Mr. Wollaston a basket-full of 

 Madeira snails (of twenty or thirty different species), three- 

 fourths of which proved to be alive, after several months' confine- 

 ment, including a sea-voyage. Mr. Wollaston has himself told 

 us that specimens of two Madeira snails {helix papilio and tecti- 

 formis) survived a fast and imprisonment in pill-boxes, of two 

 years and a half, and that a large number of the small helix 

 turricula, brought to England at the same time, were all living 

 after being inclosed in a dry bag for a year and a half. 



But the most interesting example of resuscitation occurred to 

 a specimen of the Desert snail, from Egypt, chronicled by Dr. 

 Baird.* This individual was fixed to a tablet in the British 

 Museum, on the 25th of March, 1846 ; and on March 7th, 1850, 

 it was observed that he must have come out of his shell in the 

 interval (as the paper had been discoloured, apparently in his 

 attempt to get away) ; but finding escape impossible, had again 

 retired, closing his aperture with the usual glistening film ; this 

 led to his immersion in tepid water, and marvellous recovery. 

 He is now (March 13th, 1850) alive and flomishing, and has sat 

 for his portrait. (Eig. 2.) 



The permanency of the sheU-bearing races is effectually pro- 

 vided for by their extreme fecundity ; and though exposed to a 

 hundred dangers in their early life, enough sm'vive to re-people 

 the land and sea abundantly. The spawn of a single doris may 

 contain 600,000 eggs (Darwin) ; a river-mussel has been 

 estimated to produce 300,000 young in one season, and the 

 oyster cannot be much less prolific. The land-snails have fewer 

 enemies, and, fortunately, lay fewer eggs. 

 * An. Nat. Hist. 1850. 



