302 NATURAL HISTORY. 



comb. These cells are filled with a jelly-like substance, and under the 

 control of the animal these batteries can give a very severe electrical 

 shock. The exact way in which the electricity is generated no one knows, 

 but its physical and chemical effects have been studied. The dorsal surface 

 of the torpedo is positive, and the ventral negative, and by connecting the 

 two by means of wires with suitable apparatus a spark may be obtained 

 and some chemical compounds may be decomposed. 



The appropriateness of the names torpedo and cramp-fish is very 

 evident, for bathers who have stepped upon them have been disabled by 

 the discharge. On our shores these forms are comparatively rare, and 

 nowhere do they appear to be very abundant. About fifteen species are 

 known from the whole world, three occurring in the waters of the United 

 States. 



The sting-rays, from their greater abundance, are a much more serious 

 annoyance to bathers. They have on the base of the tail a number of 

 spines, which, when trodden upon, will severely lacerate and wound the 

 foot. No one has yet been able to find any poison connected with these 

 spines, and yet the sores they cause are frequently very serious, the sur- 

 rounding surface becoming inflamed and swollen, the whole being very 

 painful and sometimes lasting for a long time. These sting-rays are not 

 all confined to the ocean ; they are also found in the fresh waters of Cen- 

 tral and South America, and Bates records their presence a thousand 

 miles up the Amazon, where they frequently injured the bathers. 



Largest and most feared of all the rays are the eagle-rays and sea-devils 

 of the tropics. They are huge monsters fifteen and twenty feet aero—, 

 which haunt the bottom, and feed upon everything found there. They 

 have a curious pair of fins growing out from the side of the head, and 

 these almost take the place of hands. With them they scoop up shells 

 and crabs and pass them to the mouth, and it is said that they occasionally 

 clasp the anchors of small boats with these fins, and drag boat and all out 

 to sea. On the west coast of America, especially at the pearl-fisheries of 

 Panama and farther south, these animals are dreaded far more than sharks 

 by the divers. These men say that the sea-devils swoop down upon them, 

 and envelop them with their broad bodies as with a blanket, and then 

 devour their victims at leisure. 



As showing the size of these devil-fishes we may be allowed to intro- 

 duce the measurements of one, the capture of which was described by Le 

 Vaillant. It was taken with harpoons, and was the smallest of three 

 which were seen. It was twenty-eight feet in length from the tips of the 

 horns to the end of the tail. Its mouth was large enough to take in a 

 man with perfect ease. It was covered with the sucking-fish, or remoras, 



