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 

 FIG. 114. -Ending extremity, as a curled, rod- 

 of electro-motor like, motor end-organ (Fig. 



SlKZS* "4)- The electric surfare 

 process of an eiec- thus faces posteriorly. 



The cytoplasm Q f 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 |g 

 of the plate shows, in transection, a layer f-g 

 similar to that seen in Mormyrus, and almost jpj 

 equally distributed on both surfaces. A few .; 

 granules of peculiar quality with some very ( o r .:, 

 few coarse fibrils can be seen in the cytoplasm 

 near the nuclei (Fig. 115). 



This electroplax has been though* 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- 



troplax of Malap. 

 terurus. (After 



BALLOWITZ.) 



Malapterurus. Rods shown on 

 ]* surfaces. (After BALLO- 



