LUMINOUS ANIMALS 143 
Not until the year 1750 was the true cause 
discovered. 
Of the various kinds of luminous fish, one 
of the most remarkable is Aethoprora effulgens , 
a deep-sea species that inhabits tropical waters 
at a depth of ten thousand feet. This finny 
light-bearer is endowed with quite an array 
of luminous points, the principal one being 
situated on the snout, and acting as a veritable 
44 head-light.” A closely-set row of minor 
lights is also present along the body on either 
side, and beneath these are others that look 
as if they were arranged in hanging loops from 
those above. 
Another species, the black astronesthes, 
found only in the Atlantic, has a double row 
of luminous spots along the body, while, 
moreover, it is also curious in the fact that it 
possesses two dorsal fins, one of which is 
composed entirely of fat. Little is known 
of the habits of this fish, and, according to 
Mr. Bullen, only half a dozen of them have 
ever been captured. 
One of these was taken from the stomach 
of a halibut that had been captured eighteen 
thousand feet below the level of the sea. 
Coccia ovata , another luminous fish, has 
twenty-five small, pearl-coloured and light- 
emitting disks upon its body, each one being 
