64 THE FAITNA OF THE DEEP SEA 



The occurrence of this blue colour in Crustaceans 

 of the deep sea is very remarkable, for blue is a colour, 

 as Moseley pointed out many years ago, that is rarely 

 met with in the fauna of the abyss, and it is certainly 

 very exceptional in "the Crustacea of that zone. 



Among the deep-sea Echinoderma we find a 

 wonderful variety of coloration. Moseley says that 

 many deep-sea Holothurians, for example, are deep 

 purple, and Agassiz reports that in one species the 

 colour was of a delicate green tinge. ' We obtained,' 

 he adds, ' a white Cucumaria and some species of 

 Benthodytes of the same colour,' while others vary 

 from transparent milky white to yellow and light 

 yellowish brown and even pinkish colours. The 

 Crinoids are described by the authorities to be white, 

 purple, yellow and brownish-chestnut, and of the 

 other groups of the echinoderms we read that the 

 star-fishes are, as a rule, of duller colours than the 

 Crustacea, but all more or less pink or red. ' The 

 Hymenasteridaa, on the contrary, vary from light 

 bluish violet to deep reddish chestnut colours.' The 

 brittle stars are red and orange or dullish grey, 

 while the urchins maybe deep violet, claret coloured, 

 brownish, or of a delicate pink. 



It is impossible to account for this extraordinary 



