366 EEPORT— 1897. 



most readily obtained by the addition of a small quantity of "5 per cent, 

 hydrochloric acid to the potassic ferrocyanide. Ammonium-hydrogen 

 sulphide gives also an immediate reaction with the green pigment. 

 Ammonia strikes a beautiful blue wherever there is green. It was then 

 found that pure hsematoxylin is an extremely delicate test, giving an 

 immediate blue reaction in exceedingly dilute solution. Previous treat- 

 ment of the green colouring matter by 3 per cent, nitric acid in alcohol 

 prevented these reactions, and subsequent treatment with acidulated 

 potassic ferrocyanide resulted in a very faint general prussian blue coloura- 

 tion of the tissue generally. We concluded that there was no inoi'ganic 

 iron present in the leucocytes, that the leucocytes which form the green 

 patches contain a considerable quantity of copper, and that, just as in the 

 case of iron, as shown by Professor Macallum,^ pure hematoxylin is a 

 most delicate test, but that great care must be taken to ascertain by other 

 reagents which of the metals is present. Very numerous tests were 

 made with the blood obtained from white oysters, and micro-chemical 

 reactions revealed in some instances faint traces of copper. Hsemocyanin 

 has been described in the blood of molluscs and apparently in the blood 

 of the oyster. We have examined numerous samples of blood taken from 

 the white oyster, but have failed to get any blue colouration on exposure 

 to air. In the green oysters a very faint blue colour has been noticed in 

 some cases on exposing the blood to air. 



Cause of the Pigmentation. 



There can be no doubt that Ryder,* in America, about 1880, investi- 

 gated the same kind of green oyster with which we are dealing. He 

 showed that the green colouring matter was taken up by the amoeboid 

 blood-cells, and that these wandering cells containing the pigment were 

 to be found in the heart, in some of the blood-vessels, and in aggregations 

 in ' cysts ' under the surface epithelium of the body. He describes the 

 colour (in the ventricle) as a ' delicate pea-green,' and states that it is 

 not chlorophyll nor diatomine ; he suggests that it may be phycocyanin 

 or some allied substance. We have now shown that it is due to a copper 

 compound. 



We consider that Ryder came nearer to what we now consider to be 

 the truth than any previous investigator has done. He was trying to 

 show that the colour was derived from the food. Carazzi has recently 

 suggested that the colour (this, it must be remembered, is in the Marennes 

 oyster), due to iron, is derived from the bottom on which the oyster is 

 lying. We have tried numerous experiments in feeding oysters on iron and 

 copper salts, both soluble and insoluble, of various strengths, and also in 

 keeping oysters on a bottom of iron or copper salts — including rusty iron, 

 old copper, and copper filings — but in none of these experiments (the full 

 details of which we shall publish later) have we got sufficiently consistent 

 and continuous results to enable us to determine whether or not the animal 

 obtains its copper from the contents of the alimentary canal or from the 

 water through the surface of the body. These experiments and observa- 

 tions are still being carried on. 



' Quarterly Journal of Microscopical Science, 1896; and Brit. Assoc. Rep., 1896, 

 p. 973. 



■■' U.S. Fish Commission. Keports and Bulletins from 1882 to 1884. 



