408 MANUAL OF ZOOLOGY. 



many well-known and useful fishes. It is divided into two 

 groups, according as ventral fins are present or not. In the 

 first group Apoda there are no ventral fins ; and the most 

 familiar examples are the common Eels of our own country. 

 The Eels (Murcenidfz] have an elongated, almost cylindrical, 

 body, with the scales deeply sunk in the skin, and scarcely ap- 

 parent. A swim-bladder is generally present, and the operculum 

 is small and mostly enveloped in the skin. More remarkable, 

 however, than the ordinary Eels is the Gymnotus eledricus, 

 or great Electric Eel, which inhabits the marshy waters 

 of those wonderful South American plains, the so-called 

 "Llanos." This extraordinary fish (fig. 172) is from five to 

 six feet in length, and the discharge of its electrical organs 

 is sufficiently powerful to kill even large animals. The fol- 

 lowing striking account is given by Humboldt of the manner 

 in which the Gymnoti are captured by the Indians : " A 



Fig. 172. Electric Eel (Gymnotus tlectricun). 



number of horses and mules are driven into a swamp which is 

 closely surrounded by Indians, until the unusual disturbance 

 excites the daring fish to venture an attack. Serpent-like, 

 they are seen swimming along the surface of the water, striving 

 cunningly to glide under the bellies of the horses. By the 

 force of their invisible blows numbers of the poor animals are 

 suddenly prostrated; others, snorting and panting, their manes 

 erect, their eyes wildly flashing terror, rush madly from the 

 raging storm ; but the Indians, armed with long bamboo staves, 

 drive them back into the midst of the pool. 



" By degrees the fury of this unequal contest begins to 

 slacken. Like clouds which have discharged their electricity, 

 the wearied eels disperse. They require long rest and nourish- 

 ing food to repair the galvanic force which they have so 

 lavishly expended. Their shocks gradually become weaker 

 and weaker. Terrified by the noise of the trampling horses, 



