SUPPLEMENT. 121 3 



effect upon breeding oysters that might be exercised by 

 heavy floods, and opened out a wide field for further 

 enquiry. 



THE CHEMICAL CONSTITUENTS AND THE FLAVOUR 



OF OYSTERS. 



The heaviest portion of an oyster is its shell, and this, 

 on an average, constitutes about 84 per cent, of the total 



weight of an ordinary Holstein table-oyster 



The dried shells of very old oysters weigh from 250 to 320 

 grams. In such heavy, thick-shelled oysters, the soft por- 

 tion is generally very poor, and the body-space is smaller 

 than at the time when it first attained its complete matu- 

 rity. From this it follows that the edges of the last-formed 

 ^hell-layers do not pass over those which were formed 

 earlier, but lie under them. The principal constituent of 

 the shell is carbonate of lime, which forms about 96 to 97 

 per cent, of the whole weight. The shell also contains 

 i '2 to 1*3 per cent, of sulphate of lime, 0*09 per cent, of 

 phosphoric acid, 0^03 per cent, of oxide of iron, and traces 

 of magnesia and aluminum. If these inorganic constitu- 

 ents of the shell are dissolved in acid, there will remain 

 undissolved brownish bits and flakes of an organic sub- 

 stance which has been named conchyolin. This contains 

 the elements oxygen, hydrogen, nitrogen, and carbon. 

 The left or arched valve of a Holstein oyster contains from 

 i -oi to 1*025 per cent, of conchyolin, the right somewhat 

 more, from no to 1*15 percent. This increase in the 

 percentage of conchyolin makes the right valve less brittle 

 than the left. 



. . . . Nearly all mussels have more beautiful 

 shells than that of the oyster, but in delicacy and fineness 

 of flavour the oyster surpasses every other mollusk. Only 



