XIII 



ELECTRIC ORGANS 



365 



associate particular sounds with the possession of dangerous 

 spines, and warned by the sounds, they refrain from attacking 

 the owner of the spines, to the mutual advantage of both. 



Electric Organs. 

 — Electric organs 

 capable of generat- 

 ing more or less 

 powerful electric 

 discharges are pre- 

 sent in certain 

 Fishes, both marine 

 and freshwater. 

 They occur in a 

 few Elasmobranchs 

 (species of Baia, 

 Torpedo, and 



Eypnos), in such 

 Teleosts as the 

 African Silurid 

 Malojpterurus, the 

 "Electric Eel" 

 (Gymnotus), and in 

 species of Mormy- 

 ridae (e.g. Mor- 

 myrus). With one 

 exception electric 

 organs are com- 

 posed of metamor- 

 phosed mus- 

 cular fibres, and 

 their nerve-endings 

 or motor end- 

 plates. The species 

 of Baia have two 

 small electric 

 organs, one on each 



Fig 209.— An Electric Ray {Torpedo) dissected to show its 

 electric organs. On the left the nerves supplying the 

 organ are dissected out. The prismatic areas on the 

 surface of the organ indicate the vertical columns of 

 electric plates, of which there may be 500,000 in each 

 The dorsal surface of the brain is exposed, br, 

 o.e, electric organs ; t. mucus 



organ. 



Gills; / spiracle; 0, eye; .-, ,- , . , ,, 



canals ■, tr, tri-geminal nerve ; tr\ its electric branch , 

 V, vagus ; J, fore-brain ; //, mid-brain ; //J, cerebellum ; 

 iv, electric lobe of the medulla oblongata. (From Parker 

 and Haswell, after Gegenbaur.) 



side of the terminal portion of the tail.^ In Gymnotus' the 



X Ewart, Phil. Trans. 179 (.), 1888, pp. 399, 410, and 539 ; 183 (b), 1893, p. 389^ 

 » Ballov;itz, ^rc;.. Mikr. Anat. 1. 1897, p. 686 ; Carl Sachs, Untersuchungcn an. 

 Zitteraal, Leipzig, 1881. 



