THE. INDIAN OCEAN. 31T 
which, while the animal is alive, are seen to dilate 
and contract with a very rapid pulsation. The little 
globe is propelled in any direction by a jerking mo- 
Nocrmvca Muinzarts, greatly magnified. 
tion of the tail or stem; and as it is a restless crea- 
ture, it is not a very easy matter to obtain a good 
sight of it for observation. 
Several species of fishes 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 Egyptian fish (Heterotis Nilotica) emitted such 
a vivid light as he never saw equalled by any other 
fish, alive or dead. And Mr. F. D. Bennett discovered 
a new species of Shark, which he named Squalus 
JSulgens, from the whole surface of whose body pro- 
ceeded a greenish light, which rendered the animal 
the most ghastly object imaginable. But there can 
be no doubt that the main source of oceanic efful- 
212 
