i8 COLOUR IN NATURE chap. 



Among Echinoderms phosphorescence seems to 

 be known only among the Ophiuroidea, where it has 

 been described both in Mediterranean and in Atlantic 

 species. 



Among the Crustacea phosphorescence is exceed- 

 ingly common, especially among deep-sea forms. In 

 some cases the luminosity is confined to the eyes, in 

 others, as in many of the deep-sea Schizopoda, there 

 are special luminous organs placed behind the eyes 

 or above the legs, in other cases again the phosphor- 

 escence is diffused. 



In the terrestrial Anthropods phosphorescence is 

 known among various insects, glowworms, fireflies, 

 etc., and among centipedes, but it is not so common 

 as among marine forms. 



Among the Mollusca phosphorescence occurs 

 among pelagic forms such as Phyllirho'e, and among 

 burrowing forms such as Pholas, whose luminosity 

 has long been known. 



Next to the Ccelentera the Tunicate are perhaps the 

 forms which display the most universal and brilliant 

 phosphorescence. Every one knows Moseley's de- 

 scription of the brilliancy of the light emitted by 

 Pyrosoma, the phosphorescent fire -flame. Many 

 other pelagic Tunicates display the same pheno- 

 menon to a lesser degree. The Tunicates display so 

 many striking analogies to the Ccelentera that this 

 physiological one is perhaps not remarkable. 



Finally, we have the phenomena of phosphores- 

 cence admirably displayed in fishes, especially the 

 pelagic and abyssal forms. In the pelagic forms 

 the sense-organs and the lateral line are often phos- 

 phorescent, while in some cases there are special 



