136 COLOUR IN NATURE chap. 



been reinvestigated since Moseley's work. Moseley 

 found antedonin also in a deep-sea Holothurian. 



S. Among tiie Holothuria black or brown pig- 

 ments are widely distributed, and may be identical 

 with those occurring in the Crinoid Holopus and the 

 dark-coloured Ophiuroids. In addition, numerous 

 bright pigments occur, but are rarely important in 

 the production of surface coloration. Among them 

 lipochromes are probably common, especially in 

 internal organs. In Ocnius brunneus, according to 

 M'Munn (1889), the ovaries are pale blue, turning 

 red and yielding a lipochrome when treated with 

 alcohol and other reagents. This is an interesting 

 case, for it seems to be the only one mentioned in 

 the literature in which an identity with Crustacean 

 pigment can be definitely maintained. 



Relations to Pigments of Crustacea 



Looking at the pigments of Echinoderms as a 

 whole, we must remark, first, the prevalence of lipo- 

 chromes, especially in the star-fishes and brittle-stars 

 where they seem to form the predominant pigments. 

 Again, the case just mentioned suggests that the blue 

 Crustacean pigments — the so-called lipochromogens 

 — are found also in Echinoderms, though there is as 

 yet no evidence to prove that they give rise to 

 external colours. 



So far, there is an analogy with the Crustacea, 

 but we find further that the pigment called entero- 

 chlorophyll is common in the digestive caeca, in 

 the perivisceral fluid and probably elsewhere in 

 Echinoderms, while in Crustacea it is, at most, rare. 



