ON THE LIFE CONDITIONS OF THE OYSTER. 



567 



The copper was also determined in the gills and in the bodies minu 

 gills of French, Dutch, and American oysters with the following results : — 



Determinatio7i of Copper. 



These data show conclusively that the green colour of the gills of 

 French oysters is also in no Avay connected with the copper present. 



Quantities of copper greater than those recorded point to abnormal 

 conditions. Such have been found to occur with certain Falmouth oysters 

 and in an especially interesting manner with the green leucocytosis of 

 American and Fleetwood oysters — the diseased condition referred to 

 above. 



Falmouth Oysters. — The presence of relatively large quantities of copper 

 in Falmouth and other Cornish oysters has been repeatedly associated with 

 their bluish-green colour. Dr. T. E. Thorpe ^ states that these oysters, 

 the colour of which, both in character and distribution, is quite different from 

 that of the Marennes oysters, contain on the average about 1-3 mgrme. of 

 copper per oyster. This large proportion is, Dr. Thorpe says, ' obviously 

 caused by the mechanical i-etention of cupriferous particles.' On relaying 

 they lose their colour, and the quantity of copper present becomes normal, 

 0'4 mgrme. per oyster. 



Six Falmouth oysters, the bodies of two of which were of a distinct 

 arsenic-green colour, were dried at 100° C, and then digested with water 

 and subsequently with dilute hydrochloric acid. The extract contained 

 about half the total copper present, showing that the metal is partially, 

 at any rate, mechanically retained on or in the body of the oyster, prob- 

 ably as a basic carbonate. 



The analytical results w^ere as follows : — 



The total copper present is almost nine times the normal quantity, and 

 about half of this is easily removed by dilute acid. It is quite likely that 

 the remainder is partially or wholly simply entangled in the food passages 

 of the oyster, and that the green colour may be due to some other cause 

 than this mechanically retained copper, as suggested by Herdman.- Mr. 

 G. C. Boui-ne, indeed, regards it as due, in some Falmouth oysters, to a 

 green desmid upon which the oysters feed in quantity.-'' 



' Nature, 1896, p. 107. " md-, 1897, p. 36G. 



-■* See Note by Mr, Bourne below, p. 569. 



