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 
