SEA-FISHERIES LABORATORY. 79 



which in mass have a green tint. These cells are granular 

 and amoeboid. The granules do not give any definite 

 reaction with the aniline stains and so far we have not 

 made out their precise nature. 



Dr. Charles Kohn, at our request, has kindly made a 

 further Chemical analysis of Oysters from various localities 

 for us, and his results, as expressed in a paper he read on 

 the subject at the British Association Meeting, are as 

 follows : — * 



" The early observations of Berthelot which showed 

 that the green colour of French oysters (' huitres de Mar- 

 ennes ') is not due to chlorophyll, but probably to iron 

 have been recently extended by A. Chatin and A. Muntz 

 (Compt. Rend., 1892, cxviii. 17 and 56). From their analy- 

 tical results these observers conclude that both the green 

 and the brown colourations of various types of French 

 oysters are due to the presence of iron, and that the depth 

 of colour bears a close proportion to the quantity of iron 

 contained. The colourations are chiefly apparent in the 

 gills, but extend also to the labial palps and parts of the 

 alimentary canal. Chatin and Muntz base their conclu- 

 sions in the first place upon the fact that they find about 

 twice as much iron in the gills as in the rest of the body 

 of green oysters, and secondly upon the occurrence of a 

 larger quantity of iron in the gills of green than of white 

 oysters. 



" The cause and origin of this colouration is a physiologi- 

 cal problem of much interest, but the confirmation of 

 Chatin and Muntz' results also appeared of importance 

 to Profs. Herdman and Boyce in connexion with their 

 investigations on oysters and disease, and therefore the 



* I beg to express my thanks to Dr. Kohn for his kindness in making 

 these determinations for us, and for allowing me to incorporate his results in 

 this report. 



