340 SEA-SIDE STUDIES. 



to contract, lias passed away. The men take advantage of 

 this to exercise the oysters, and make them accustomed to be 

 out of water, by removing them daily into the atmosphere, 

 and leaving them there for longer and longer periods. This 

 has the desired effect ; the well-educated mollusc keeps his 

 shell closed for many consecutive hours, and as long as the 

 shell is closed his gills are kept moist. 



The ten days of my Cockle sink into insignificance be- 

 side the astonishing facts on record. In Mr Woodward's 

 valuable Manual of the Mollusca, we read : " The fresh- 

 water mollu.scs of cold climates bury themselves during 

 winter in the mud of their ponds and rivers ; and the 

 land-snails hide themselves in the ground, or beneath the 

 moss and dead leaves. In warm climates they become torpid 

 during the hottest and driest part of the year. Those genera 

 and species which are most subject to this summer sleep are 

 remarkable for their tenacity of life, and numerous instances 

 have been recorded of their importation from distant coun- 

 tries in a living state. In June 1850, a living pond-mussel 

 was sent to Mr Gray from Australia, which had been more 

 than a year out of water. The pond-snails have been found 

 alive in logsof mahogany from Honduras : and M. Cailland car- 

 ried some from Egypt to Paris packed in sawdust. Indeed, it is 

 noteasy to ascertain the limit of their endurance ; for ]\Ir Laid- 

 lay, having placed a number in a drawer for this purpose, 

 found them alive after five years, although in the warm 

 climate of Calcutta. Mr Wollaston has told us that speci- 

 mens of two IMadeira snails survived a fast imprisonment in 

 pill-boxes of two years and a half. But the most interesting 



