M. BEvnATUT oft 'Mohscce.- §f 



fresh-water with fresh-water moluscae ; or, on the other 

 hand, tliat fresh-water moluscae could live in salt-water, 

 with marine moluscae. 



This hypothesis received some support from facts long 

 known to naturalists. Many species of marine moluscas, 

 especially oysters, cerithia, and common muscles, are knowii 

 to live at the mouths of rivers, and evpn at distances from 

 the sea, where the water is fresh, or at least but rarely 

 salt ; many marine fish are also known to mount rivers to a 

 still more considerable distance from the sea, where they 

 Can never be under the influence of salt-water. .' 



" The contrary, i, e. the presence of fresh-water moluscae, 

 or animals in the sea, does not appear to have been ob- 

 served ; nothing is known in this respect but some vague 

 notices of fresh-water fish living in the waters of the Baltic. 

 * It was of consequence to verify this double hypothesis in 

 a more precise manner ; with this view M. Beudant under- 

 took many series of experiments, an account of which he 

 had the honour of presenting to the Academy of Sciences. 

 The object was : 1. to endeavour to make fresh-water mo- 

 luscjB live in salt-water : 2. to habituate marine moluscae 

 to live in fresh-water. Two other subsidiary objects werfe 

 also proposed : 3. to search for the cause of the almost to- 

 tal absence of fossil shells in the gypsum bedsc and 4. the 

 cause of the moluscae and other organized bodies, living in 

 the Asphaltic lake, whose waters contain, according to 

 Lavoisier, 0,44 of saline matter, of which there is only 0,06 

 of muriate of soda. 



■ He commenced his experiments on fresh-water raolusca 

 at Paris, in 1808 and 1809 : and it was not until 1813 that 

 he could execute those on marine moluscae at Marseilles. 



He employed in the whole many hundred individuals, of 

 which he had previously determined the species ; he kept 

 a regular journal of his observations, and especially of the 

 number and species of the individuals that perished at 

 different times. "" 



Being obliged to keep these moluscae in vases, where they 

 ■were necessarily much confined, and to nourish them with 



