EXPERIMENTS IN FEEDING WITH METALLIC SALTS. 33 



found to be alive and healthy, with the heart beating actively, and no green or brown 

 staining in any part. The rest were opened on March 26th, and found to be in the 

 same healthy condition. 



Dr. Kohn then made us up some soluble salts, and on May 27th two batches of 

 oysters were put in tanks of sea-water containing a small amount of chloride of copper. 

 On June 4th, three were found to be dead, and on examining these one had a slight 

 greenish tinge over the viscera and a green spot in its heart, and the second had a 

 good deal of green over the right side of its mantle, and many of its vessels were 

 engorged with pale green leucocytes. The third specimen was not green, and in none 

 of them was there any greenness in the gills. Twenty of these same oysters, opened at 

 the beginning of the experiment, showed only one slightly green specimen. On June 

 5th, another specimen from the copper solution showed a greenish mantle, and the 

 following day the remaining five oysters, when opened, were found to be all more or 

 less tinged with green — as follows : — 



A. Green on mantle over viscera, and slightly on mantle over gills. Heart very 



green and chalky. 



B. Green on mantle over gills, and heart slightly so. 



C. Green on mantle over gills, and heart very green. 



D. Very green on mantle over gills, and slightly over viscera. Heart pea-green. 



E. Slightly green on mantle over gills and over viscera. Heart pale chalky green. 



The gills themselves were scarcely affected in any case. In the case of the 

 mantle, the staining was not on the surface, but in the leucocytes in the tissues and 

 blood spaces. 



A second batch started on June 5th, in the same soluble copper salt, were opened 

 on June nth and 12th, when it was found that all had their hearts more or less green, 

 and the mantle over the viscera stained, and having blood-vessels engorged with green 

 leucocytes. Most of them had the mantle over the gills stained of a greyish-blue 

 colour. The gills themselves were not affected in any case. A control batch of four 

 of the same oysters kept in ordinary sea-water showed, however, one heart very green 

 and the other three slightly so. One had the vessels over the viscera engorged, and 

 there was a little green staining in the mantle of all. 



It was evident, then, that these oysters were becoming green to some extent, 

 quite apart from any action of the copper, but those in the copper solution were 

 decidedly greener than the control oysters. On June 12th, some further experimental 

 batches were started, (A) in ordinary sea-water, (B) in a solution of the same copper 

 salt in which 10 c.c. was added to the gallon, and (C) another in which i c.c. was 

 added per gallon. On June 18th, (A) showed four normal oysters, and one specimen 

 a little green in the heart ; (B) showed one specimen normal, and four all somewhat 

 green ; (C) showed three with no green, two with engorged vessels containing green 

 leucocytes, and one of them with a green heart. 



