73 



quantity of iron, which is evidently normally present, the 

 gills containing a somewhat larger amount in proportion 

 to the total quantity of mineral matter present. 



' Finally, the total iron in a variety of Oysters wa.s 

 determined in order to ascertain the normal quantity 

 present. These data, which are tabulated below, show a 

 fairly constant proportion of iron per Oyster, from 0"15 to 

 0"36 mgrme., or from 0"18 to 065 per cent, on the ash. 



Total Iron present in Oysters. 



Variety of Oyster 



'Ilultres 

 rennes ' 

 Dutch 

 American 

 Collie 

 Deep Sea 

 Falmoutli 



de Mar- 



Weight of 

 Ash. I 



Mgrme. 



Iron 



l>er 

 Oyster. 



0-7860 

 1393 

 0-2791 

 1-0938 

 1-5017 

 0-4534 



0-30 

 0-15 

 0-36 

 0-20 

 0-32 

 27 



Percent- 

 age of 

 Iron on 

 Ash. 



0-23 

 0-65 

 0-64 

 0-18 

 0-43 

 0-35 



' In considering the variations in quantity, the very small 

 amounts of metal present must be borne in mind. 



* It may be added that although Carazzi has attributed 

 the green colour of French Oysters to iron taken up from 

 the mud of the Oyster-park or " claire," experiments on 

 feeding Oysters with very dilute solutions of iron salts 

 (0"02 to O'Ol per cent.) carried on in conjunction with 

 Prof. Herdman produced no green colouration whatever. 

 The only result was a certain amount of "browning" 

 throughout the Oyster, the gills being no more affected 

 than the rest of tlie body. More recently Carazzi has 

 shown that Oysters fed with similar dilute iron solutions 

 acquire a pale yellowish colour in certain parts (branchial 

 epitliclium and the oesophageal mucous membrane), and 



