38 AMKRICAN FISHKRIES SOCIETY. 



if a meinbratieous sac holding salts in solution is immersed in a 

 more dilute solution or impure water, the more concentrated so- 

 lution will pass out and at the same time the water or more dilute 

 solution will pass in and nuHc rapidly. Tlie escape of the con- 

 centrated and entrance of the dilute solution will be, in general 

 tlie more rapid the greater the difference in concentration and 

 the higher the temperature of the two solutions. After the os- 

 miose has proceeded for a time, the two solutions will become 

 equally diluted. When this equilibrium between the two is 

 reached the osmose will stop. If the sac which has become dis- 

 tended is elastic, it will, after osmose has ceased, tend to come 

 back to its normal size, the extra quantity of solution which it 

 has received, being driven out again. 



We should expect these principles to apply to the oyster. 

 Roughly speaking, the body of the animal may be regarded as 

 a collection of membraneous sacs. It seems entirely reasonable 

 to suppose, that the intercellular Spaces and probably the cells 

 of the body would be impregnated with the salts of the sea-water 

 in which the animal lives, and this supposition is confirmed by 

 the large quantity of mineral salts which the body is found by 

 analysis to contain, and which amounts, in some cases, to over 

 14 per cent, of the water-free substance of the body. 



It seems equally reasonable to assume that osmose would take 

 place through both tlie outer coating of the body and the cell 

 walls. In the salt water the solution of salts within the bodv 

 may be assumed to be in equilibrium with the surrounding me- 

 dium. When the animal is brought into fresh or brackish water 

 i.e., into a more dilute solution, the salts in the more concen- 

 trated solution within the bodv would tend to pass in and pro- 

 duce just such a distension as actually takes place in the floating. 

 If this assumption is correct, we should expect that the osmose 

 would be the more rapid the less the amount of salts in the sin- 

 rounding water; that it would proceed more rapidly in warm 

 and more slowly in cold water; that it would take place whether 

 the body of the animal is left in the shell or is previously re- 

 moved from it; that the quantity of salts would be greatly 

 reduced in floating; and that if it were left in the water 

 after tlie maximum distension had been reached, the imbibed 



