FISHES. 257 



feriorly by membrane, and the heart, invested in 

 pericardium, is lodged within it, as in a box or cell. 



When the larger specimen, taken at night, was re- 

 moved into a dark apartment, it afforded a very ex- 

 traordinary spectacle. The entire inferior surface of 

 the body and head emitted a vivid and greenish phospho- 

 rescent gleam, imparting to the creature, by its own 

 light, a truly ghastly and terrific appearance. The 

 luminous effect was constant, and not perceptibly 

 increased by agitation or friction. I thought, at one 

 time, that it shone brighter when the fish struggled, 

 but I was not satisfied that such was the fact. When 

 the shark expired, (which was not until it had been out 

 of the water more than three hours,) the luminous 

 appearance faded entirely from the abdomen, and more 

 gradually from other parts ; lingering the longest around 

 the jaws and on the fins. 



The only part of the under surface of the animal 

 which was free from luminosity was the black collar 

 around the throat ; and while the inferior surface of the 

 pectoral, anal, and caudal fins shone with splendour, 

 their superior surface (including the upper lobe of the 

 tail-fin) was in darkness, as also were the dorsal fins, 

 back, and summit of the head. 



I am inclined to believe that the luminous power of 

 this shark resides in a peculiar secretion from the skin. 

 It was my first impression, that the fish had accidentally 

 contracted some phosphorescent matter from the sea, 

 or from the net in which it was captured ; but the most 

 rigid investigation did not confirm this suspicion ; 

 while the uniformity with which the luminous gleam 

 occupied certain portions of the body and fins, its 

 permanence during life, and decline and cessation upon 

 the approach and occurrence of death, did not leave a 



VOL. II. S 



