CHAPTER VI 
THE COLOURS OF CRUSTACEA AND ECHINODERMA 
Nature of Colours of Crustacea—Colour-variation—Pigments 
of Crustacea : (i) Lipochromes, (2) Soluble Blues—Re¬ 
lations of Two—General Characters of Pigments—The 
Colours of Echinoderma : (1) Star-fishes, (2) Brittle-stars, 
(3) Sea-urchins, (4) Crinoids, (5) Holothurians—Pigments 
of Five Classes—Relations to those of Crustacea. 
We shall in this chapter discuss both the Echino¬ 
derma and the Crustacea—not that there is any 
morphological affinity between them, but because 
there is considerable resemblance as regards pigments. 
In both, moreover, there is a tendency for lime salts 
to be associated with the coloured regions. 
Nature of Colours of Crustacea 
The coloration of the Crustacea presents many 
points of very great interest ; the beauty of the 
colours, their adaptation to the surroundings, and 
their great variety combine to render the subject 
peculiarly attractive. 
It is unnecessary to dwell upon the general 
