loo The Ottawa Naturalist. 



electrometer or suitable apparatus was available to test the 

 electro-motive force in a Skate of such enormous dimensions. 

 The Sting Rays, with a tail exhibiting one or more strongly 

 developed spines, and the Eagle or Whip Rays with a slender 

 whip-like tail, appear to be wholly destitute of electric organs. 



Turning now to the South American electric eel, Gymnotus, 

 we find electric organs differing much from those described. In 

 these large creatures, five or six feet in length, they are lodged 

 along each side of the body towards the under side, and mainly 

 in the tail. Two pairs occur, the upper much larger than the 

 more central pair. Each organ is divided into vertical plates 

 by fibrous septa, and again into a countless number of small 

 cells, arranged horizontally, instead of vertically as in the tor- 

 pedo. The shock passes laterally from the head to the tail, and 

 no less than two hundred pairs of spinal nerves send electric 

 rami into the organs. The combined result is exceedingly 

 powerful. A captive Gyimiotus exhibited in London some time 

 ago, was able to kill its victims at a considerable distance. It 

 fed upon fish, and when one of the victims was dropped into the 

 tank, the Gymnotus simply curved slightly, stiffened its body, 

 and a shock was communicated through the water which struck 

 the introduced fish lifeless with lightning rapidity. 



Another form of electric organ is that found in the African 

 s\\\ixc)\^, Malapterurus, a fish not remotely related to our mud- 

 pouts and cat-fishes, to which it bears much external resem- 

 blance. A layer of cells, lozenge-shaped and about one-sixteenth 

 of an inch in diameter, extends between the skin and the under- 

 lying muscles except in the region of the head and the fins. 

 Just as in Gymnotus, the current passes from the head to the tail. 

 It is comparatively feeble, and probably only defensive. In- 

 stead of a nerve supply consisting of many thousands of fibres, a 

 single nerve trunk passes from the spinal cord to the organ on 

 each side of the body. The Nile is the home not only of the 

 electric Siluroid Malapterurus, but of the electric Nile pike 

 Morniyrus. There are many species of Mormyrus and, in all, 

 the electric organs are somewhat feeble and located mainly in 



