ANIMAL ELECTRICITY AND PHOSPHORESCENCE. 85 



the total (without caudal). Jaws equal in front. The outer mandibnlary 

 barbels extend to the root of the pectoral. Body with more or less numerous 

 small roundish black spots, a part of which are sometimes confluent into 

 larger irregular patches ; anal and caudal fins with a white margin. Dorsal 

 vertebrae 17 ; caudal 22. 



Habitat. Nile, and rivers of the west coast of Africa. 



The only organ that can be regarded as connected with the electrical 

 function in this fish is a thick layer of dense connective tissue which com- 

 pletely surrounds the body immediately beneath the integument. So com- 

 pact is it that, at first sight, it might be mistaken for a deposit of fatty 

 matter; but, under the microscope, it appears to be composed of tendinous 

 fibres, closely interwoven, the meshes of which are filled with a gelatinous 

 substance. This organ is divided by a strong aponeurotic membrane into 

 two circular layers, one outer, lying immediately beneath the derm, the other 

 internal, placed above the muscles. Both organs are isolated from the sur- 

 rounding parts by a dense fascia, excepting where the nerves and blood- 

 vessels enter. The cells or meshes in the outer organ, formed by its reticu- 

 lated fibres, are rhombic in shape, and very minute, so as to require a lens 

 to see them well. The component tissue of the inner organ is somewhat 

 flaky, and also cellular. 



The nerves of the outer organ are branches of the fifth pair, which runs 

 beneath the lateral line and above the aponeurotic covering of the organ. 

 This aponeurosis is pierced by many holes for the transmission of the nerves, 

 which are lost within the cellular tissue of the organ. The intercostals 

 supply the inner organ ; their electrical branches are numerous and remark- 

 ably fine. (Coldstream.) 



M. Beninsis, M. Affinis. Species closely resembling above. Habitat. 

 Old Calabar. (Giinther.) 



Of the electrical power of Tetraodon electricus and Trichiu- 

 rus electricus, as well as Scolopendra clectrica, little is known. 



Animal electricity presenting so many features in common 

 with that derived from inorganic sources, was at one time 

 believed to be identical with it. The idea originated with 

 Galvaui, who discovered that by bringing a current in- 

 duced by placing two metallic plates one of copper and 

 the other of zinc in contact with the nerve of a leg of a 

 dead frog, contraction of its muscles ensued. (Galvanism.) 

 He inferred from this that he had re-supplied the force re- 

 moved by death, and that the nervous power and the agent 

 he had employed were convertible. Ilis opinion received 

 apparent confirmation from the fact that all electrical organs 



