PHOSPHORESCENT FISHES 135 



clearest detail. Aristmts coruscans, of which only one 

 specimen, a female, was obtained, also emitted from 

 the same place similar clouds of light, which, how- 

 ever, were less abundant and less brilliant than those 

 of Heterocarpus. The green glands correspond in 

 function with kidneys, so that if, as seems to be the 

 case, the excreta of these two prawns are luminous, 

 the fact is by no means an isolated one. The light 

 displayed by the female of Pentackeles phosphorus was 

 a steady glow at two points near the openings of the 

 oviducts, where there was found to be a greasy, gland- 

 ular patch, very much like that seen in the same place 

 in the females of several species of Indian prawns of 

 the genus Peneus, 



In this haul we also obtained specimens of a curious 

 jet-black deep-sea fish belonging to a family (^Ophidiidce) 

 related to the cod-fishes, the scales of whose ''lateral 

 line," or ''slime-canal," are greatly enlarged and modi- 

 fied to produce light. The scales in question are all 

 embedded in a continuous sheath of particularly black 

 skin, which, however, is loop-holed opposite every 

 scale, to expose a spindle-shaped cavity, filled with a 

 greasy, opaque-white secretion, dug in the scale itself 

 The secretion probably oxidises slowly — the oxygen 

 in all probability coming, not from that dissolved in 

 the seawater, but from that contained in the blood 

 itself — so as to produce a cold phosphorescent light. 

 When all its lamps are shining, the fish must have 



