144 Papers from the Department of Marine Biology. 



single gigantic nerve-cell, with but one axis cylinder, the branches of 

 which reach all of the somewhat over 72,000 compartments in each 

 half of the organ and are estimated to have a peripheral distribution 

 unsurpassed by that of any other single nerve-cell (Gotch 5o). 



In all the other electric fishes the organs are divided into columns, 

 themselves subdivided at regular intervals by connective-tissue septa 

 and fixed at their peripheral edges by the boundary wall. Each of 

 these compartments contains a protoplasmic mass, the electroplax, in 

 which the efferent nerves end, while the rest of the space is occupied by 

 the transparent material. The essential elements are much the same in 

 all. The protoplasmic mass with its supporting fibers, cross-striations, 

 and nerve terminations is called the electric plate, electric disk, or elec- 

 troplax. The nerves on coming in contact with the electroplaxes branch 

 in a characteristic dichotomous manner in most of the groups. 



In Raja hatis a band of parallel wavy fibers crosses the transparent 

 area, still possessing the optical properties common to ordinary stri- 

 ated muscle-fibers and representing the vestiges of the cross-striation of 

 the voluntary muscle-fibers, from which, according to Ewart and 

 Engelmann (39 and 4i), the electric plate has been derived. This layer 

 will be termed the striated layer for convenience in this paper, although 

 the striations are no longer wholly comparable to those of muscle- 

 tissue and although they have almost entirely disappeared in Gymnotus 

 and Torpedo, the strongest of the electric fishes. In Torpedo there is 

 a faint fibrillation in each electroplax during its early embryonic state, 

 which is completely resorbed during development. In Gymnotus and 

 in Malopterurus no indication of the striations is visible even in the 

 earliest stages yet seen. It is therefore evident that the loss of definite 

 striation is correlated with the gain in electrical power and it is possible 

 that the evolution of the electric organs may follow the loss of the 

 original muscle striations. 



PHYSIOLOGICAL. 



Perhaps the best-known of all the investigators of electric fishes is 

 DuBois-Reymond. The founder of electro-physiology^, he has ex- 

 haustively covered the subject of electrical currents in muscle, nerves, 

 and electrical organs, carrying on, in the early eighties, a prolonged 

 dispute with Hering (57) and Hermann (58, 59) concerning the extent of 

 polarization arising in a muscle when an electrical current has been 

 passed through it. DuBois-Reymond experimented on living Malop- 

 terurus and on living Torpedo in Berlin, and under his direction Sachs 

 worked on living Gymnotus in South America. Their combined results 

 are so comprehensive and so accurate as to leave room for no further 

 investigation of the same nature, and the name of DuBois-Reymond is 

 recognized to be that of the leader in the physiological researches on 

 animal electricity. 



