I52 A NATURAL HISTORY OF THE SEAS 



pass cannot be properly understood until the ocean 

 depths have been more thoroughly surveyed. 



As previously mentioned, the prevalent colours of deep- 

 sea fishes appear to be black or bright red, both sufficiently 

 inconspicuous in a world from which the last light has 

 vanished. The abyss, however, it is now known, is not 

 entirely the world of Stygian darkness it was once assumed 

 to be. Fishes, Corals, Hydroids and a myriad other 

 creatures light the darkness with an eerie radiance. 

 Luminous organs vary from mere collections of light cells 

 generating a luminescent slime to complex batteries, the 

 light from which is augmented by lenses and reflectors 

 which parallel to a remarkable degree many human 

 devices. 



The ways in which such lights may be disposed about 

 the fish are legion. In some cases the entire tegument 

 of the fish is invested, but more frequently the lights are 

 localised. Some fishes carry their light organs ranged 

 in rows along their sides, so that the creature suggests a 

 finer as seen at night with every port-hole brilliantly illumin- 

 ated. Often the light organs take the form of immense 

 headlights arranged before or behind the eyes ; or again 

 they may be mounted on special rod-like organs. Certain 

 small abyssal Sharks have the whole of the undersurface 

 illuminated so that the fish, which are bottom-feeders, 

 light up the sea-bed as they travel, their lights probably 

 serving the double purpose of a lure and a means of 

 locating animals tempted from their burrows. Light 

 organs reach their highest development in the bony fishes, 

 and in some the reflector is so powerful that it still functions 

 when the animal is actually dead. 



