VI COLOURS OF CRUSTACEA AND ECHINODERMA 137 



Associated probably with the presence of this 

 pigment we find numerous bright-coloured integu- 

 mentary pigments, which may be of the nature of 

 derivatives, as well as complex pigments like ante- 

 donin and pentacrinin whose relations are more 

 doubtful. 



Another point of contrast with the Crustacea is 

 the prevalence of dark pigments, which, though most 

 characteristic of Holothurians, tend to appear more 

 or less frequently in the other groups. 



