THE INDIAN OCEAM. 359 



very easily obtained for microscopic exaniinatioii 

 It occurs by millions on the surface of the summer 

 sea — more abundantly in some seasons than in 

 others — and may be easily scooped up with a basin. 



NOCTTT.UCA MTLiARis, magnified. 



The animals will be found, when the vessel is at 

 rest, accumulated at the surface, especially around 

 the edge, where they frequently form a layer of five 

 or six deep. "With care they may be preserved for 

 above a week without changing their sea-water. 



Several species of fislies are undoubtedly lumi- 

 nous : the Sun-fish (Cephalus mola), when seen at a 

 considerable distance below the surface in a dark 

 night, is said to glow like a cannon-ball heated to 

 whiteness. Ehrenberg found that the whole skeleton 

 of an Eg}^ptian fish (Heterotis Xilotica) emitted such 

 a vivid light as he never saw equalled by any other 



