ANIMAL ELECTRICITY. 

 Fig. 48. 



91 



The right electrical organ divided horixontatty at the place where the nerves enter, the upper half 



being turned outwards. 



A A, The first or anterior electrical nerve. 



B B, The second or middle nerve arising behind the gill. 



C C, The anterior branch of the third nerve arising behind the second gill. 



D D, The posterior branch of the third nerve arising behind the third giU. 



which, probably, serves as a medium of com- 

 munication between the electrical organs ; being, 

 apparently, a better conductor of electricity 

 than either the naked skin or salt water.* 



With regard to the development of the elec- 

 trical organs, it appears that, in the earliest 

 stages of foetal growth, they cannot be seen. In 

 a foetus of about seven-tenths of an inch in 

 length, Dr. Davy found neither electrical organs 

 nor fins. In another, more than one inch long, 

 the organs were beginning to appear, and the 

 roots of the electrical nerves were visible, 

 although the brain could not be seen. In this 

 stage, the external branchial filaments were 

 about six-tenths of an inch in length, and pre- 



* Davy, Phil. Trans. 1832. Also Annales du 

 Mas. no. v., in which E. Geoffroy endeavoured to 

 show that the common mucous system of rays is 

 absent in the torpedo, and that its place is supplied 

 by the columns of the electrical organs, which he 

 believed to be analogous to the mucous ducts. 



sented a very remarkable appearance. In a 

 foetus of two inches and a half long, the electrical 

 organs were distinctly formed, and the branchial 

 filaments still long. These filaments Dr. Davy 

 supposes to be destined to absorb matter for the 

 formation of the electrical organs, and, perhaps, 

 the gills and adjoining mucous glands. They 

 are most numerous and of greatest length while 

 the electrical organs are forming, appearing just 

 before these organs begin to be developed, and 

 being removed when they are tolerably com- 

 plete. In no other allied fishes is there the 

 same " elaborate apparatus of filaments;" 

 where they do exist, they are less numerous and 

 very much shorter. 



2. The electrical organs in the Gymnotus. 

 This fish has a general resemblance in form to 

 the common eel. Its electrical organs occupy 

 nearly one-third of its whole bulk. They are 

 formed by two series of tendinous membranes ; 

 one of which consists of horizontal plates, run- 



