Adaptations of Fishes 



187 



of electric fishes, is not an eel, but allied rather to the sucker or 

 carp. It is, however, eel-like in form and lives in rivers of Brazil 

 and Guiana. The electric organs are in two pairs, one on the back 

 of the tail, the other on the 

 anal fin. These are made up 

 of an enormous number of 

 minute cells. In the electric 

 eel, as in the other electric 

 fishes, the nerves supplying 

 these organs are much larger 

 than those passing from the 

 spinal cord for any other pur- 

 pose. In all these cases 

 closely related species show 

 no trace of the electric powers. 



Dr. Gilbert has described 

 the electric powers of species 

 of star-gazer {Astroscopus 

 y-grcccinn and A. zcpliyrcits), 

 the electric cells lying under 

 the naked skin of the top of 

 the head. Electric power is 

 ascribed to a species of cusk 

 (Uropliycis rcgius), but this 

 perhaps needs verification. 



Photophores or Luminous 

 Organs. — ^lany fishes, cliiefly 

 of the deep seas, develop 

 organs for producing light. 

 These are known as luminous 

 organs, phosphorescent or- 

 gans, 01 photophores. These 

 are independently developed 

 in four entirely unrelated 

 groups of fishes. This differ- 

 ence in origin is accomjianied 

 by corresponding difference in structure. The best-known 

 type is found in the Iniomi, including the lantern-fishes and 

 their many relatives. These ma}^ have luminous spots, differ- 



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