110 MANUAL OF NATUKAL HISTORY. 



The electric apparatus is placed along the under 

 side of the body, extending from behind the pec- 

 torals to the tail. The organs are four in number, 

 two on either side, and one above the other, the 

 upper ones being the larger. The organs of one 

 side are separated from those of the other by the 

 vertebral column, its muscles, the air-bladder, and an 

 aponeurotic septum, from which last, and from one 

 covering the air-bladder, extend outwards to the 

 skin numerous horizontal membranes, arranged in 

 the longitudinal axis of the body. These are inter- 

 sected transversely by more delicate vertical plates, 

 which thus form cells, filled with a pellucid liquid. 

 The battery is thus horizontal ; and it has been 

 shewn by Faraday, that the electric current is al- 

 ways from the anterior to the posterior parts of the 

 animal. In this fish the electric organs are supplied 

 by the ventral branches of all the spinal nerves.* 



19. FAMILY. Eels (Mursenidse). Body serpentiform ; 



scales very small, enveloped in a mucous 

 epidermis; branchial spiracles two, lateral, 

 placed one on each side ; ventral fins wanting. 



20. FAMILY. Sub-branchial Eels (Synbranchidse). 



Body anguilliform ; spiracles two, or in some 

 one, placed under the throat. (Symbranchii, 

 MulL) 



XL ORDER SUCTORIAL-FISHES (Dermopteri). 

 Endo-skeleton unossified ; exo-skeleton, and ver- 

 tical fins muco-dermoid ; vermiform, or abrachial, 

 and apodal ; no pancreas ; no air-bladder. 



* See Owen's " Lectures on Comparative Anatomy," vol. ii, p. 213. 



