ELECTRICAL ORGANS IN FISHES. 293 



The posterior of these is a delicate, wide-meshed, fibrous layer, 

 in which alone the nerves ramify ; the anterior consists of 

 a thicker layer of the peculiar vascular, dotted, nucleated 

 texture which forms the laminae in Torpedo. Both surfaces 

 of the vasculo-cellular layer present an arrangement of pro- 

 minent, close-set, undulating ridges, with thick, rounded, 

 nucleated margins. The ridges are more fully developed on 

 the anterior than on the posterior surface of the layer, and 

 from the ridges of the latter a number of thread-like pro- 

 longations pass backwards through the interposed fluid to the 

 fibro-nervous layer, so as to connect the two layers as one 

 compound lamina. From the measurements and calculations 

 of Pacini, the superficial extent of the anterior surface of the 

 vasculo-nucleated layer is increased by this rigid structure 

 from five to six times, the posterior about twice. 



The electro-motor series, therefore, in Gyrnnotus, instead 

 of simple laminae, as in Torpedo, consist of compound laminae 

 separated by layers of fluid. There are thus two kinds of 

 fluid in the electro-motor series of Gymnotus firstly, that 

 between the vasculo-cellular layers and the fibro-nervous, 

 and which must be considered as an element of each com- 

 pound electric diaphragm ; and, secondly, that between any 

 two electric diaphragms, which is the homologue of the fluid 

 layer in Torpedo. 



As the current in Gymnotus passes from before backwards, 

 Pacini denominates the vasculo-cellular layer the positive, and 

 the fibro-nervous layer the negative element, of the electro- 

 motor series. 



The batteries in Malapterurus are two in number, sepa- 

 rated, but at the same time intimately connected to one another 

 in the mesial plane, along the dorsal and ventral margins of 

 the body, so as to form a continuous layer of a gelatinous 

 consistence, closely adherent to the skin, and enclosing as in a 

 sac the entire animal, except the head and fins. In the 



