er en na 
THE ELECTRIC ORGANS OF FISHES. 153 
ing in some species (Raia batis and Raia maculata) a 
comparatively small number of highly differentiated trans- 
verse plates arranged in series. The electrical effects 
produced by the discharge of this organ are incapable, 
as far as we know, of producing any obvious physiological 
effects upon other living fish in the neighbourhood of the 
skate. 
In conclusion the lecturer brought before the notice of 
the audience the following considerations bearing upon 
the question as to the extent to which the apparently 
anomalous functions of an electric organ are merely an 
exaggeration of activities common to all other animals. 
These may be grouped as follows :— 
A. From embryological evidence each plate of the 
columns of the Torpedo and the Skate organs appears to 
be partly homologous with a striated muscle fibre and 
partly with the ending in the fibre of a motor nerve, 
the former portion 1s however reduced to very small amount 
whilst the latter part is very much increased in complexity. 
-B. The plate of every electrical organ is so constructed 
when fully formed that the nervous supply is limited to 
one side of the disc. On this side is a rich plexus of 
entering nerve fibres which divide dichotomously into a 
‘large number of finer nerve fibrils; these penetrate the 
deeper substance of the plates and appear to end blindly 
in it. 
C. Inall electrical organs the character of the electrical 
change which accompanies its functional activity is such 
that the innervated surface of each plate becomes galvan- 
ometrically negative to the other surface, in other words 
the electrical current which is produced and forms the 
shock, passes through the plate from the side the nerve 
enters to the deeper substance and out by the side free 
from nerves. 
