71 



iron, both in the gills and in the rest of the body, 

 shows a marked increase, apparently corresponding to the 

 depth of the colouration. The iron was determined in 

 these experiments by potassium permanganate, but the 

 absolute quantities of metal found are not stated. The 

 calculation of the results per 100 parts of dried organic 

 matter is apt to be misleading. In my own experiments 

 it was not found possible to get anything approaching 

 constant weights in this way, and the results are entirely 

 out of accord with those of Chatiii and Muntz. 



* The following table gives the quantities of iron found in 

 French as compared with American Oysters, three pairs 

 of gills being analysed in each case. 



' These figures show conclusively that there is more and 

 not less iron in the gills of the white American Oysters 

 than in the French, and this irrespective of the basis on 

 which the result is calculated. The ash is undoubtedly 

 the most reliable factor to calculate on, provided the 

 Oysters are carefully w^ashed before drying, which was 

 always done : the result per pair of gills (or Oyster) is 

 most in accord with this, and has the advantage of being 

 an easy and in many respects useful basis. 



