120 



HISTOLOGY 



The other feature appears to be unique, and consists of a series of 



peculiar pointed fibers and long, pointed rods lying in the cytoplasm of 



the electric layer. The use of these structures, which are shaped like the 

 classic " thunderbolts," is unknown. They might pos- 

 sibly be elongated " rods " such as are found in the 

 other forms. Figure 112, from doubtful material, 

 shows a possible thin nutritive layer which may be 

 an artifact. 



Malapterurus has developed its electric cell in that 

 part of its integument which surrounds the middle 

 region of the body. The large, round, flat electroplaxes 

 occupy a vertical position facing forward and backward, 

 as in Gymnotus and Mormyrus. The surface of one 

 of these plates is moderately regular, with the excep- 

 tion of the single large evaginated process which 

 reaches backward from an anteriorly bent and cup- 

 shaped area of the middle of the plate. This process, 

 which is as long as a quarter of the diameter of the 

 plate, is met by the motor nerve, which ends in its 

 extremity, as a curled, rod- 

 like, motor end-organ (Fig. 

 114). The electric surface 

 thus faces posteriorly. 



The cytoplasm of the elec- 

 troplax is very lightly reticular 

 and somewhat granular, and 



the large nuclei are much less numerous than 



in most other forms of the organ. The edge 



of the plate shows, in transection, a layer 



similar to that seen in Mormyrus, and almost 



equally distributed on both surfaces. A few 



granules of peculiar quality with some very 



few coarse fibrils can be seen in the cytoplasm 



near the nuclei (Fig. 115). 



This electroplax has been thought to be a 



development of a gland cell in the skin of the 



fish. The writers cannot agree with this, and 



consider it to be, more probably, a specialized 



smooth muscle cell of the dermis, or even derived from a layer of the 



striated body musculature. The embryology and histogenesis of this 



electric organ should be made the subject of investigation at the 



earliest opportunity. 



Technic. The same as for the other electric tissues. No embryo- 



FIG. 114. Ending 

 of electro-motor 

 nerve fiber on the 

 end of the central 

 process of an elec- 

 troplax of Malap- 

 terurus. (After 

 BALLOWITZ.) 



Malapterurus. 

 both surfaces. 



W1TZ.) 



Rods shown on 

 (After BALLO- 



