XIV 
ORIGIN OF PIGMENTS 
299 
fuse pigmentation of the epidermis and cuticle, and 
there is certainly a marked elimination of pigment 
in the shell at the moult. The elimination of intro¬ 
duced pigment by the skin in the Capitellidae is 
regarded as evidence that the pigment naturally 
occurring there is a waste product, but the applica¬ 
tion of the same principle to the Crustacea is fraught 
with obvious difficulties. If conclusions are to be 
drawn from the fate of introduced pigments, then 
the pigment of the cuticle in Crustacea is not a waste 
product; if, on the other hand, it is the elimination 
of pigment by a moult which is the criterion, then 
the pigment is a waste product. 
As a whole, therefore, it would seem that while it is 
impossible for a physiologist to conceive of pigment 
being produced in the organism in the haphazard 
fashion some would have us believe, yet it is at 
present also impossible to give a universal physio¬ 
logical explanation of its origin ; it probably arises in 
many different ways. As yet the classification of 
pigments given in the second chapter cannot appar¬ 
ently be simplified. 
