34 THE DEPTHS OF THE SEA 



fishes, notably of members of the Stomiadse, a family 

 allied to the salmons. From head to tail the miniature 

 bull's-eyes extend, like so many portholes lit up, with 

 sometimes one or two larger organs in front of the 

 eyes, like the port and starboard lanterns of a ship, so 

 that when one of these fishes swims swiftly across the 

 dim scene it must, to quote Kipling again, recall a 

 liner going past ' like a grand hotel.' Sometimes the 

 phosphorescent organ is at the tip of a barbel or 

 tentacle, and it is interesting to note that the angler- 

 fish of the deep sea has replaced its white lure, con- 

 spicuous in shallow water, but invisible in the dark, 

 by a luminous process, the investigation of which 

 leads many a creature into the enormous, toothed 

 mouth of the fish. 



A peculiar organ, known by the name ' phseodaria,' 

 exists in the body of certain radiolarians found only 

 in the deep seas. It has been suggested that this 

 structure gives forth light ; and, if this be the case, the 

 floor of the ocean is strewn with minute glow-lamps, 

 which perhaps give forth as much light as the surface 

 of the sea on a calm summer's night. There is, how- 

 ever, much indirect evidence that, except for these 

 intermittent sources, the abysses of the ocean are 

 sunk in an impenetrable gloom. 



When physical conditions change, living organisms 

 strive to adapt themselves to the changed conditions. 

 Hence, when the inhabitants of the shallower waters 

 made their way into the darker deeps, many of them, 

 in the course of generations, increased the size of their 

 eyes until they were out of all proportion to their 

 other sense-organs. Others gave up the contest on 

 these lines, and set about replacing their visual organs 

 by long tactile tentacles or feelers, which are extraor- 

 dinarily sensitive to external impressions. Like the 

 blind, they endeavour to compensate for loss of sight 

 by increased tactile perception ; and in these forms 



