226 On Molluscce. 



proper for determining the gradual transition of the sea molluscs 

 in fresh water, also formed two series of the same species. He 

 preserved one constantly in sea water, and employed for the other 

 sea water diluted successively with fresh water. Five months 

 afterwards he employed nothing but fresh water. 



By means of this precaution, the marine molluscse were habi- 

 tuated to fresh water, in which they lived during five months 

 more with lymnaeae and planorbes. There were some peculiar 

 circumstances attending them, which M. Beudant relates ; viz. 



The patellae of the vulgar species, and the sabots, which are 

 both sea shore shellfish — the cerites, the columbellse, the vc- 

 nuses, the oysters, &c. perfectly resisted the experiment. There 

 died thirty-four out of the hundred individuals constantly kej)t 

 in sea water, and thirty-six out of the hundred of those exposed 

 to fresh water. 



But the dragon-headed patellae, the fissurellie, the crepidulse, 

 the undated buccinae, the cameos, &c. all died during the ex- 

 periment. It ought to be remarked, however, that all the species 

 lived perfectly well in sea water diluted with an equal portion of 

 fresh water, i. e. in water containing about 0*02 of its weight of 

 salt. 



Having learned by Lavoisier's analysis that the waters of lake 

 Asphaltus contained 0*40 of saline substances*, and as accord- 

 ing to travellers no organized living body is to be found in it, 

 M. Beudant was desirous of knowing what degree of saltness 

 marine animals could support. Consequently he added impure 

 muriate of soda to common sea water, and he was convinced 

 that all the sea molluscae which he had at his disposal lived, 

 without any apparent inconvenience, in water containing 0-3 1 

 of saline matter composed chiefly of muriate of soda, with some 

 centimes of muriate of lime and muriate of magnesia. But as 

 often as h.e increased the quantity of salt, so as that small crystals 

 were formed on a slight evaporation in the air, the animals 

 shrunk within their shells, and died. 



M. Beudant concludes by drawing the following inferences: 



I. Since there is every reason to believe that the same water, 

 whether fresh, or salt like that of the sea, or even salter, is ca- 

 pable of support'ng all the animals which frequent marshes, 

 rivers, and the sea-shore, it may be presumed that similar cir- 

 cumstances have existed in nature, and to these circumstances 

 it is owing that we see in one and the same stratum sea and 



* Lavoisier's analysis gave Water - - . ■ _ 5560 



Muriate of soda - - - _ 6-25 



Muriate af lime £Uid muriate of magnesia 38' 1» 



loooa 

 land 



