ELECTRIC ORGAN OF THE SILURUS. o5 



to it, composed of thin and crossed layers, mois- 

 tened with a gelatinous fluid, doubled at its inner 

 aspect by a silvery looking aponeurosis, to which 

 it also strongly adheres. Under this aponeurosis 

 the great vascular and nervous trunks are distri- 

 buted, their branches penetrating, to be distributed 

 upon the overlying tissue. Besides this there is 

 the second tunic, which M. Rudolphi described; 

 but this, instead of being quite simple, as that cele- 

 brated anatomist supposed, M. Valenciennes found 

 was composed of at least six folds or layers, 

 which in every respect resemble each other, but 

 are altogether distinct, and may readily be sepa- 

 rated from the subjacent muscles, to which they 

 are attached only by loose and not very abundant 

 cellular membrane. These aponeurotic layers ex- 

 tend to the caudal fin, and are thin, dense, and 

 extensible under the finger ; their external surface 

 becomes flocculent by the imbibition of water. 

 These tufts, which resemble moist cotton, exhibit, 

 under high magnifying powers, a felt of fibres which 

 are extremely minute, and interlaced among them- 

 selves. The tunics receive upon their external aspect 

 very delicate fibres of the nerve, running beneath 

 the aponeurosis ; others, arising from the intercos- 

 tals, also very fine, pass to the six membranes and 

 are distributed on their internal surface. These de- 

 tails supply, we believe, all the information which 

 can be derived concerning the electric organs of the 

 Malapterurus^ so far as they can be learned from 

 anir*''ls preserved in alcohol. It is inferred, that 



