xXUI 
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 Lava, 
Torpedo, and 
Hypnos), in such 
Teleosts as the 
African Silurid 
Malopterurus, the 
mlecinic. Hel” 
(Gymnotus), and in 
species of Mormy- 
ridae (eg. . 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 Raia have two 
small electric 
organs, one on each 
side of the terminal portion of the tail.’ 
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 
organ. ‘The dorsal surface of the brain is exposed. br, 
Gills ; f, spiracle ; 0, eye; 0.e, electric organs ; ¢, mucus 
canals ; ¢r, tri-geminal nerve ; 7’, its electric branch ; 
vy, vagus ; J, fore-brain ; 7/7, mid-brain ; ITT, cerebellum ; 
IV, electric lobe of the medulla oblongata. (From Parker 
and Haswell, after Gegenbaur.) 
In Gymnotus* the 
1 Ewart, Phil. Trans. 179 (B), 1888, pp. 399, 410, and 539 ; 183 (B), 1893, p. 389. 
2 Ballowitz, Arch. Mikr. Anat. 1. 1897, p. 686 ; Carl Sachs, Intersuchungen am 
Zitteraal, Leipzig, 1881. 
