CHAPTER V 
COLOUR-PHENOMENA IN WORMS 
Colours of Turbellaria and Nemertea—Pigments of Gephyrea— 
Colours of the Chsetopoda, Structural and Pigmental 
Colours — The Pigments of the Capitellidae — General 
Characters of Coloration of Leeches and Origin of Mark¬ 
ings—Pigments of Polyzoa and the Origin of Pigmentation. 
As central and unspecialised forms, the worms are 
of considerable interest in a comparative study of 
colour, and there are several interesting facts in 
regard to them which make it desirable that we 
should consider the more important groups suc¬ 
cessively. 
The somewhat grim associations which cluster 
about the Platyhelminths do not lead us to expect 
bright colours among them, and yet in point of fact 
the free living forms often exhibit great brilliancy. 
Among the Turbellaria pigment frequently occurs 
in the cells of the epidermis, in the interstices between 
these cells, or in the parenchyma of the body. 
Many, such as Convoluta, contain in the cells of this 
parenchyma the so-called symbiotic Algae of green 
or brown colour. These chlorophyll cells have no 
cellulose envelope, and often contain pyrenoids. 
