754 KEPOKT OF COMMISSIONER OF FISH AND FISHERIES. [6] 



but tliese mollusks did not live as long as the preceding ones. They suc- 

 cumbed a mouth after they had been placed in the solutions, first in the 

 salts of potash, then in the salts ol magnesia, and finally in the salts of 

 soda. 



The periwinkles resisted longer than the bivalves, and showed less 

 repugnance to sulphate of soda, in which they lived forty days. 



The great buccin succumbs much quicker, as it canno:^ close its shell 

 hermetrically like the periwinkles. At the end of twenty-four days it 

 died in most of the solutions employed, especially in the salts of potash. 

 Its life was prolonged forty-eight hours in solution No. 12, in the sul- 

 phate of magnesia, and in the sulphate of soda, but soon came to an 

 end. 



During all the time these experiments were going on, from January 

 10 to March 15, the palourdes and the periwinkles lived in the sea-water 

 of the laboratory, the Venus reticulata and the mussels not quite so 

 long, and the buccins only a few days. 



It is a very important fact, to which we direct special attention, that 

 the salts which constitute the sea-water and the different solutions 

 which we employed gave to the water the faculty of dissolving variable 

 quantities of atmospheric air. We proved by direct experiments that 

 the solutions of salts of soda retain more air when agitated by it than the 

 solutions of salts of potash. This Avould, therefore, prove that the 

 poisonous character of the salts mentioned in our experiments is caused 

 in part by the circumstance that they do not let their solutions be- 

 come sufiiciently aerated ; their action produced asphyxia. This explains 

 why the sulphate of potash and the sulphate of soda, neutral salts to 

 which the mollusks are by no means adapted, act so differently upon 

 them, the salts of potash killing them quickly and the salts of soda 

 preserving them for some time. 



From these experiments the following conclusions have been reached: 



1. The saline elements of the sea- water act very differently on mol- 

 lusks. 



2. Every modification in the composition of the sea-water finally be- 

 comes fatal to the life of these animals. 



3. Their greater or less resistance depends on their organization. Bi- 

 valves resist better than spiral shells, and in these two groups the re- 

 sults vary according to the different species. 



4. Salts of potash are less favorable to the life of mollusks than salts 

 of magnesia; and salts of magnesia are less favorable than salts of 

 soda. 



5. Outside of the salts dissolved in sea-water the sulphate of soda 

 seems to possess a well-established preserving neutrality. 



G. The death of the bivalves is caused by a general weakening of the 

 muscles. 



7. As the muscles can no longer either draw together or open the 

 valves, the animal is exposed to the unfavorable or poisonous action of 

 the element. 



