98 JAMES G. HUGHES, JR. 
middle layer, and a lower or nutritive layer which along with 
the middle layer is evaginated into a large number of long 
papillae. All three layers are deeply marked with a dense 
series of fine striations, which are peculiar to the electroplaxes 
of several other fishes. The upper or electric surface is flat 
and smooth and receives the nerve endings. The current of 
electricity runs downward through the organ which produces 
it, and thus the nerve endings in accordance with Pacini’s law 
are found on the negative pole of the electroplax. 
Proceeding directly to the subject of this paper, we may say 
that one of the most interesting of the points noted in the elec- 
troplaxes, when properly fixed and stained with iron hematoxy- 
lin, is a series of rod-like or thread-like objects running hori- 
zontally in the electric layer, among, above and below the nuclei 
and without any apparent connection with them (figs. 1 and 2).? 
These rods are of various sizes and shapes, and in form are said 
to resemble the classic thunderbolts seen in the hand of rep- 
resentations of Jove. They usually taper slowly and branch 
extensively at one or both ends. Some of these branches some- 
times seem to be mere lines, while others are wide and heavily 
pointed; at their other ends the rods are usually rounded; this 
latter appearance may be due, however, to the cut ends of the 
rods, for as noted above they sometimes branch at both ends. 
Some are short and heavy in appearance while others are long 
and thread-like. Peculiar looping, twisting, or knot-like bends 
are sometimes found at points on the longer rods. The out- 
lines and contour of these rods are always smooth. Their size 
may vary from thick or thin rods of over 300 u in length down 
to small ones that do not exceed 1 uw. In those electroplaxes 
where the rods are few they sometimes lie parallel and point 
in a definite parallel direction, while in others where the rods 
are very numerous they do not seem to have any definite 
arrangement. In this latter condition the rods present a very 
Wavy appearance. Their form may be seen in figures 1 and 2, 
which are drawings of the electric layer of an electroplax when 
* All the figures are drawings of sections of electroplaxes of Astroscopus 
guttatus. 
