IX THE COLOURS OF INVERTEBRATES 195 



one waged over the question whether lobsters are 

 black or red ! They find that, altogether apart from 

 the famous Marennes oysters, there occurs in diseased 

 oysters a green colour due to the presence of a large 

 amount of copper. Drs. Boyce and Herdman do 

 not believe that the large increase in the amount 

 of copper normally present is necessarily the result 

 of the presence of copper in the food, but "are 

 inclined to suggest that it may be due to a disturbed 

 metabolism, whereby the normal copper of the hsemo- 

 cyanin, which is probably passing through the body 

 in minute amounts, ceases to be removed, and so 

 becomes stored up in certain cells." There is every 

 reason to believe that such "green oysters" are 

 highly poisonous, while the Marennes oysters are of 

 course quite harmless. The paper thus settles a 

 time-honoured controversy in the most satisfactory 

 manner. 



Characters of the Coloration of 

 Invertebrates 



With the Mollusca we end our study of the colours 

 and colouring-matters of the Invertebrates. As a 

 whole the Invertebrates are characterised by the 

 number and diversity of their pigments, which in the 

 simple forms occur in connection with internal organs 

 and are often very variable ; by the frequent beauty of 

 their structural colours ; and in the case of the more 

 differentiated forms in certain groups, by the beauty 

 of their patterns and markings. In Vertebrates the 

 pigments are less numerous, often less vivid, and the 

 beauty is usually dUe either to structural colour or 



