PRODUCTION OF LIGHT 415 



row of phosphorescent spots near the ventral edge extending 

 from the chin to the tail. Astronesthes, on the other hand, 

 though in its long teeth and in the presence of a long barbel on the 

 chin it has the characters of a bathybial and ground-haunting fish, 

 has frequently been obtained at the surface, but it was also re- 

 corded by the Challenger from 2500 fathoms. It seems possible 

 that true deep-sea fishes are occasionally carried to the surface 

 in some way not well understood, and it is difficult in many cases 

 to be sure whether a species is naturally pelagic or only occurs at 

 the surface accidentally. Astronesthes has luminous organs in 

 two rows along each side near the ventral edge, a luminous patch 

 higher up on the side behind the head, two patches beneath the 

 eye on the upper jaw and another central patch on the forehead. 

 In 1854 the emission of light by living specimens of Astronesthes 

 was twice observed by Professor Reinhardt. The specimens 

 were captured at the surface in the Atlantic between 6° and 23 N. 

 Lat., where they are fairly common and they gave out a strong 

 and vivid greenish light which occasionally ceased for a moment 

 and then reappeared. The fish soon died and then the light 

 ceased altogether. Numerous species of the type genus Stomias 

 are known ; they have mostly been taken from depths of less 

 than a thousand fathoms in the Atlantic, the Indian Ocean, and 

 the Pacific. They are long, slender, snake-like in shape with 

 large head and large mouth and teeth : they have a double 

 row of luminous organs on each side as in Astronesthes, and a 

 well-developed barbel on the chin. 



Malacosteus is an extraordinary form with an enormous 

 mouth, the gape extending backwards beyond the bases of the 

 pectoral fins. There is a strong elastic cord attaching the 

 tongue to the middle of the lower jaw to prevent rupture of the 

 mouth by the large prey which the fish swallows. There is a 

 large crescentic luminous patch below the eye and another a little 

 farther back. The colour is black with minute white spots 

 scattered over the body which may also be luminous. The Chal- 

 lenger specimen was taken at 500 fathoms near the Philippines ; 

 other specimens of closely allied species have been taken in the 

 Atlantic at depths over IOOO fathoms. Another peculiar fish of 

 this family is Idiacanthus, called Bathyophis by Giinther. It is a 

 very slender elongated fish with a somewhat enlarged head and 

 mouth and a long barbel on the chin. It has a small luminous 



