422 



ZOOLOGY. 



two inches) long. Raja eglanteria Lacepede (Fig. 391) 

 ranges from Cape Cod to the Caribbean Sea. The smaller 

 figures in Fig. 391 represc-nt respectively the mouth and 

 gill-slits, and the jaws of Myliobatis fremenvillii Lesueur. 



In the torpedo the body is somewhat oval and rounded. 

 Fig. 392 represents Torpedo marmoratus, of the Mediter- 

 ranean Sea. 



Our native species, found mostly in winter, especially 



on the low sandv 



* 



shores of Cape Cod, 

 is Torpedo occiden- 

 tal is Storer. Its bat- 

 teries and nerves are 

 substantially as in 

 the European spe- 

 cies. The electrical 

 organs are construct- 

 ed on the principle 

 of a Voltaic pile, 

 consisting of two 

 series or layers of 

 hexagonal cells, the 



space between the 

 numerous fine trans- 

 verse plates in the 

 cells filled Avith a 

 trembling jelly-like 

 mass, each cell 

 representing, so to 



Fig. 391. Raja eglanteria, male. Mouth and gill- speak, a Leydoil jar. 

 slits, jaws and teeth of Myliubatlg fremt nvillii j . ml , ' 



There are about 4,0 



cells in each battery, each provided with nerves sent off from 

 the fifth and eighth pairs of nerves. The dorsal side of 

 the apparatus is positively electrical, the ventral side nega- 

 tively so. The electrical current passes from the dorsal to 

 the ventral side. When the electrical ray is disturbed by the 

 touch of any object, the impression is conveyed by the sen- 

 sory nerves to the brain, exciting there an act of the will 

 which is conveyed along the electric nerves to the batteries, 



