ELECTRIC TISSUES, TELEOS'TS 



119 



of flat plates or electroplaxes (Fig. 112). The parallel plates lie hori- 

 zontally in the fish's head, and the upper or electric surface of each 

 electroplax is flat and smooth and receives the nerve-endings, which are 

 somewhat like those of Raja and Torpedo in form (Fig. 113). 



The lower or nutritive layer is evaginated into a large number of long 

 papillae, which anastomose somewhat and project downward from the 

 plate for about twice its thickness. 



The nuclei are numerous and are differentiated into two groups, the 



FIG. 112. Portion of a vertical section through 

 the electroplax of Astroscopus. el. I., electric 

 layer containing the electric nuclei and the 

 peculiar fibers or rods. 



FIG. 113. Silver nitrate picture of a nerve- 

 ending on electric surface of the electroplax 

 in Astroscopus. nv.f., nerve fiber. Nerve- 

 ending is black. The reticular tissue of the 

 electric layer shows regularly arranged 

 spaces in which lie the transparent electric 

 nuclei. 



electric group lying in the uppermost of the three very faintly defined 

 layers into which the plate may be divided. These nuclei are equally 

 spaced in this layer and appear very regular in position. The second 

 set are those few remaining ones which are scattered through the lower 

 part of the electroplax, principally in the papillae. The rods have not yet 

 been certainly demonstrated in this form. 



Besides the points described above, Astroscopus has two peculiar 

 features. The entire cytoplasm of the electroplax is striated uniformly 

 with a series of fine, close-set striae that run, as in Raja, in curved parallel 

 groups. This striation is probably a vestigial indication of the muscle 

 tissue from which the electroplax was developed. 



