SEA-FISHEBIES LABOBATOBY/. 



141 



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 was 

 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 015 to 

 0*36 mgrme., or from 0*18 to 0'65 per cent, on the ash. 



Total Iron present in Oysters. 











Mgrme. 



Percent- 





Number 



Total Iron 



Weight of 



Iron 



age of 



Variety of Oyster 



Analysed . 



grme. 



Ash. 



per 

 Oyster. 



Iron on 

 Ash. 



' Huitres de Mar- 













rennes ' ... 



6 



0-0018 



0-7860 



0-30 



0-23 



Dutch 



6 



0-0009 



0-1393 



0-15 



0-65 



American ... 



5 



0-0018 



0*2791 



0-36 



0-64 



Colne 



10 



0-0020 



1-0938 



0-20 



0-18 ■ 



Deep Sea ... 



2 



0-0064 



1-5017 



0-32 



0-43 



Falmouth ... 



6 



0-0016 



0-4534 



027 



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 0*01 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 the body. More recently Carazzi has 

 shown that Oysters fed with similar dilute iron solutions 

 acquire a pale yellowish colour in certain parts (branchial 

 epithelium and the oesophageal mucous membrane), and 



