34 OYSTERS AND DISEASE. 



These are samples of a large number of similar experiments* made with different 

 salts of copper and iron, soluble and insoluble, and of various degrees of strength, which 

 give, on the whole, the following results : — 



1. In no case was any greening at all comparable with that of the Marennes 

 oysters produced. 



2. The insoluble salts which lay as a deposit at the bottom ot the aquarium 



seemed to produce little, if any, effect. 



3. The soluble salts of iron either produced no effect, or had a favourable effect, 



the oysters living rather • better in these solutions than in ordinary sea-water. 

 They gave rise to no greening. 



4. The very weak soluble copper-salts had little, if any, effect ; while the 



stronger copper-salts had always an unfavourable effect upon the life of the 

 oyster, causing death sooner or later ; and in most cases producing more or 

 less of that unhealthy green leucocytosis which we had found in various 

 kinds of oysters bedded around our coast, and which Ryder evidently found 

 amongst oysters on the American coast. 



* Since this was written we have carried out (October to December, 1898) a series of further experiments 

 at the Lancashire Sea J'isheries Hatchery at Piel Island, in the Barrow Channel. The oysters were kept in 

 tanks through which a constant current of fresh sea-water was running. To this current measured quantities of 

 dilute copper and iron salts were added drop by drop, in such a way as to mix thoroughly with the sea-water 

 before reaching the oysters. We have examined these oysters, and find that those that have been for from one to 

 three weeks in the current containing the copper solution, show evidence of having more than the normal amount 

 of copper in their bodies, but still there was no apparent greening. Those in the iron solution were unaffected. 



These experiments are being continued for us by Mr. Andrew Scott, Resident Assistant at the Piel 

 Hatchery, and will be shortly extended to mussels and cockles, which, we find, are also liable to become green. 



