206 Light 



organs occur in widely different groups. At somewhat deeper levels 

 the eyes of fish tend to be enlarged or "telescopic" and in some species 

 directed upwards. At greater depths eyes are often degenerate or 

 entirely absent. Eyes would perhaps be of little use here since 

 both daylight and animal Hght produce very meager illumination. 



N.G.S. Copyright, 1934 



Fig. 6.9. Drawing to illustrate the appearance of the photophores of the deep 



sea fish Photostomias guernei and of the luminous discharge of the shrimp 



Acanthephyra purpurea in the inky blackness of the ocean abyss. 



