389 
one of their specimens of A. guttatus that had been in the museum 
for over twenty-two years in alcohol. The electric organs of this fish 
were found to be in good condition. The tissues served to show the 
form of the electroplaxes, the striation of the iayers and the new 
structures in the neuro-electric layer, to which we hesitate to apply 
a name until it has been made the subject of fourther study. We 
wish to thank the staff of the museum for the temporary use of this 
valuble material as well as for the specimen of Urophycis regius 
(WaLBAUM) which they also kindly sent us. 
The American Museum of Natural History loaned us specimens 
that were of the utmost importance in our work; a fine specimen of 
Astroscopue y-graecum which ye ilded knowledge of the anatomy of 
the electric organ as well as confirmation of its histological structure. 
We wish here to express our thanks to Mr. G. H. SHerwoop through 
whom the museum so generously allowed us the use of their material. 
We also thank Professors MACLOSKIE, Scorr and McCuure of Prin- 
ceton University for their kind assistance in connection with our work. 
Part I. ‘Finer Anatomy of the Electric Organs. 
By ULrıc DAHLGREN. 
With Figs. 1 to 11. 
To give enough of the gross anatomy to make it possible to 
procede with a description of the tissues, I will say that the organs 
form two irregular vertical columns, roughly oval in horizontal section 
and placed symmetrically, one just behind and somewhat under each 
eye the muscles of which it most curiously involves. Each organ ex- 
tends from a peculiar bare spot on the top of the head down to the 
tissues that form the roof of the oral cavity. In diameter the organs 
are a little larger than the bare spot above mentioned (see Fig. 13, 
Part II). 
Each column or organ is composed of a large number of flat, 
thin electric plates or electroplaxes. They lie horizontally in the organ; 
flat, even and always at the same distance from one another. This 
is well shown in the vertical section of the organ that we will examine 
first (Fig. 1). One specimen of A. guttatus had in each organ 155 of 
these layers by which term I mean all the different electroplaxes that 
are found at one level. A somewhat larger specimen of A. y-graecum 
had about 200 layers. 
The peculiar jelly-like connective tissue, or electric connective 
tissue, that is characteristic of the electric tissues of other fishes, is 
also found here, lying between the electroplaxes and spacing them 
apart a distance that is about the same as their own thickness. This 
