422 



ZOOLOGY. 



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

 ranges from Cape Cod to the Caribbean Sea. The smaller 

 figures in Fig. 391 represent lespectively the mouth and 

 gill-sUts, and the jaws of Myliobatis fremenvillii Lesueui-. 



In the torpedo the body is somewhat oval and rounded. 

 Fig. 392 represents Torpedo ntarmoratus, of the Mediter- 

 ranean Sea. 



Our native species, found mostly in winter, especially 



on the low sandy 

 shores of Cape Cod, 

 is Torpedo occiden- 

 talis Stoi-er. Its bat- 

 teries and neiTes ai'e 

 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 iine trans- 

 vei'se plates in the 

 cells filled with a 

 trembling jeUy-Uke 

 mass, each cell 

 representing, so to 



Baja egZanteria, male. Month and gill- speak, a Levden iar 

 id teeth of Myliobatis fremen/viUii ? . -rii t 



ihere are about 470 

 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 su. The electrical current passes from the dorsal to 

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

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

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

 which is conveyed along the electric nerves to the batteries. 



Fi2. 391.- 

 slits, jaws and 



