194 COLOUR IN NATURE chap. 



elusions be correct, then marennin must be added to 

 the list of the pigments of Mollusca. In this con- 

 nection it is interesting to note its extreme stability, 

 a character which is rare among green pigments in 

 Mollusca or elsewhere ; the extreme vividness of the 

 tint is also very striking. 



Carazzi's statements, if well established, will over- 

 throw the view that the green oysters are coloured 

 by derived pigment, which is a point of some 

 importance. Of course there are other instances, 

 e.g. that of Mr. Poulton's caterpillars, which seem to 

 be well established and to prove the possibility of 

 pigment transference from one organism to another, 

 but we have still no means of knowing whether or 

 not this is of common occurrence in the animal 

 kingdom. The question is interesting, because 

 suggestions as to pigment transference have been 

 very freely made to explain cases of resemblance 

 between organisms and their surroundings. 



The subject of " Green Oysters " has given rise 

 to so many heated discussions that, although a 

 little apart from our main theme, we may pause 

 to note a very interesting paper by Drs. Boyce and 

 Herdman on an abnormal green pigmentation. Part 

 of the interest taken- in the general subject has been 

 due to the fact that there have repeatedly occurred 

 instances of poisoning from the eating of green 

 oysters, where the symptoms have been declared 

 to be those of copper - poisoning. On the other 

 hand, many examinations of coloured oysters have 

 failed to demonstrate the presence of copper. The 

 researches of the authors mentioned have shown that 

 the dispute presents a strong analogy to that historic 



