FISHES 1 5 5 



These fish habitually seize upon and burrow into 

 the sides of other and larger fishes, often penetrating 

 so deeply into the victim that the eyes become hidden, 

 and as a result these organs have become practically 

 little more than vestigeal. 



Surface-dwelling fishes or forms inhabiting mid-depth 

 where light generally penetrates have normally developed 

 eyes of average size ; but in the depths one is confronted 

 with what at first appears to be an anomaly. Here there 

 are fishes with gigantic eyes living side by side with others 

 having very feebly developed organs of vision. The large- 

 eyed fishes of the abyss generally have little in the way of 

 luminous organs and it is believed that they rely for 

 visibility upon the innumerable invertebrate animals, 

 which, as previously mentioned, are in many instances 

 known to be luminous to a degree. 



Light, it is now known, is not entirely absent until one 

 reaches a depth of nearly 2,000 feet, and there is no marked 

 deterioration in the eyes of fish until this depth is reached. 

 So long as light is present at all fishes appear to make use 

 of every available ray. Complete blindness is indeed 

 a very rare condition in marine fishes. An example is 

 that of the Blind Goby (Thylogobius) living on the reefs 

 fringing the shores of Southern California. Here it 

 fastens itself to the undersurface of rocks or penetrates 

 into the ready-made burrows of crustaceans. The fish 

 presents the features characteristic of animals which thus 

 seek retirement. It is small, pale in colour, has a smooth, 

 naked skin and is blind. The eyes though small are 

 present in the young ; they function normally in infancy, 

 but deteriorate into mere vestiges hidden beneath the skin 



