[3] BIOLOGICAL ACTION OF SEA-WATER UPON ANIMALS. 751 



Another solution was composed as follows : 

 Solution No. 12 : 



Chloride of sodium . . 8 



Chloride of potassium 8 



Chloride of magnesium . 8 



Chloride of calcium 8 



Besides these solutions, or means of experimentation, there were also 

 employed : 



Solution No. 13 : Natural Vichy water (Celestins). 

 No. 14 : Common water (springs at Brest). 

 No. 15 : Natural sea- water (roads of Brest). 

 No. 16 : Atmospheric air. 



The Vichy water represented an aqueous element different from the 

 sea- water, but rich in salts of soda. It was also necessary to compare 

 the action of the artificial elements with that of the natural element, 

 the sea- water, and to observe whether mollusks, well enclosed in their 

 shells, could not live for some time in fresh water, or even in the air. 



Method of experimentation. — The above solutions were poured 

 into porcelain capsules, placed in the light at an average temperature of 

 12°. Every two days the evaporated water was replaced by distilled water, 

 so as to keep the solutions in the same state of concentration. Every day 

 these solutions were strongly aerated and shaken, with the view of 

 maintaining conditions analogous to those of sea-water. Mollusks re- 

 cently caught were i)laced at the bottom of the capsules at a distance of 

 20 centimeters from the surface of the liquid. 



SuB.TEC'TS OF EXPERIMENTATION. — A Very Small number of species 

 have been subjected to these physiological experiments.* They are : 



The reticulated venus-shell ( Venus reticulata). 



The common mussel (Mytilus eduUs). 



The paJourde ( Venus decussata). 



The common periwinkle {Littorina vulgaris). 



The huccin of the British Channel {Tritonium undatum). 



By reason of their different organization these mollusks have given 

 very different results. The bivalves, mussels and venuses, which can 

 shut themselves up between their valves, have as a general rule showed 

 greater resistance than the opercular spiral -shelled mollusks, peri- 

 winkles and buccius. Of these the periwinkles, whose operculum can 

 close entirely, prudently retired into the remotest coils of the spiral, and 

 were thus better protected than the buccins, whose opening does not 

 shut tightly, and into which the water can easily enter by the canal at 

 the mouth of the shell. 



The bivalves, which can resist external intluences, whilst inclosed be- 

 tween their valv^es, do not by any means act in the same manner. In 



* Oysters, subjected to the same experiments, have sliowu great variableness of im- 

 pressions, and have generally succumbed very rapidly in the different solutions. 



