CHAPTER XXII 

 ELECTRIC ORGANS 



A GREAT many fishes are possessed of an electric organ — a curious 

 specialization found only in this class of Vertebrates. They are all developed 

 from modified muscular tissue formed into plates arranged in series ; the 

 only exception is that of the electric catfish. Malopternrus, which is developed 

 from cutaneous glands (Garten, 1910). When a muscle contracts the energy 



3r 



Fig. 901. — The Starc^zer, A-i hn^i ,,i i -. 



The electric organs are seen as the flat areas behind the eyes. The fish normally 

 lies biu-ied in the mud with only the eyes, mouth, electric plates and a fin showing, 

 so that the small fish which swim too near are electrocuted and fall straight into the 

 ugly open mouth (Alice Jane Mansueti, Chesapeake Biol. Lab., Maryland, U.S.A. : 

 from the lUust. Loud. News). 



developed is expended in motion, heat, and electricity ; in electric organs 

 the electrical properties, in jjlace of being subsidiary, become predominant. 

 Among Selachians, in electric rays {Hy2marce, Torpedo) the organ is immense, 

 running through the entire thickness of the body between the head and 

 the pectoral fin ; in other rays and in the teleostean electric eel, Electro- 

 pJiorus, it is smaller and situated at the sides of the root of the tail. In the 

 American stargazer, Astroscopus, however, the great rarity is found of an 

 electric organ situated in the orbit derived from the extra-ocular muscles, 

 all of which with the exception of the inferior rectus and the inferior oblique, 

 while retaining to some extent their original function, have become modified 



