VITALITY OF MOLLUSCS. 357 



gence, yet even the Oyster seems to be educable to a 

 small degree. Milne Edwards relates, that in the great 

 oyster establishments on the coasts of Calvados, he 

 learned that the merchants teach these succulent mol- 

 luscs to keep their shells closed when out of the water, 

 by which means they retain the water in their shells, 

 keep their gills moist, and arrive lively in Paris. The 

 process is this : No sooner is an oyster taken from the 

 sea than it closes its shells, and opens them only after 

 a certain time — from " fatigue/' it is said, but more 

 probably because the shock it received, and which 

 caused its muscles to contract, has 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 

 beside the astonishing facts on record. In Mr Wood- 

 ward's valuable Manual of the Mollusca^ we read : 

 " The fresh-water molluscs of cold climates bury them- 

 selves during mnter 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 re- 

 markable for their tenacity of life, and numerous in- 



