146 Papers from the Department of Marine Biology. 



Rajidse and the Mormyridse to those of the strong electric fishes, except 

 in the intensity of the shock. The true electrical nature of these 

 organs, which had been previously considered electrical from their 

 structure but had not been determined by experiment as to function, 

 was now ascertained, for definite electrical currents could be detected 

 by the galvanometer. 



The combined results of these investigators, notwithstanding certain 

 prolonged controversies, have led to a pretty definite agreement as to 

 the nature of the activity of these organs. The activity of the electric 

 organs is dependent upon the arrangement of the electrical plates in a 

 linear series for its adequate expression, and the columnar structure of 

 the organ thus modifies rather than determines the characteristics 

 of the activity. The nature of these activities lies in the electrical 

 change in the nerves themselves, expressed through the agency of the 

 electroplaxes. That the disk is the excitable structure responding to 

 impulses from the nerves is an abandoned theory contradicted by all 

 experimental evidence, for such paralyzing drugs as atropin and 

 curare, which are known to effectively destroy the action of muscle- 

 tissue, have no effect upon the activity of the electric organs unless 

 given in such doses as to paralyze the nerves themselves. All the 

 effects in the electrical organs are connected with excitation, and its 

 concomitant alteration, which is always accompanied in the nerve by 

 rapid electric changes, while the structural nature of the organ is such 

 that the changes in each group of nerve terminations may become con- 

 spicuous by summing with those of the neighboring groups (Gotch so) . 



Another law which has been generally accepted is that of Pacini, in 

 connection with the probable direction of the current in the different 

 electric fishes. He states that the electric current will run from the 

 electric layer where the nerve-endings are, to the nutritive layer, so 

 that the electric surface will be negative to the nutritive one. Experi- 

 ment has so far verified this law in every case which has been examined 

 in this regard, except in that of Malopterurus, in which the current 

 goes in the opposite direction, namely, from the nutritive to the electric 

 layer. 



EMBRYOLOGICAL. 



In 1877 Babuchin (4), in 1888 Ewart (40), and in 1894 Engelmann 

 (39) worked out the origin of the electric organs of Torpedo and the 

 MormyridEe, then known as the pseudoelectric fishes, showing that, in 

 general, electric organs have arisen by the modification of certain 

 striated muscle-cells. In Torpedo and the Rajidse each electroplax 

 arises from a single cell, but Babuchin has shown (2, 3) that in the 

 Mormyridse a syncytium of cells from the fibers of the sacrolurnbalis 

 muscles may go into the formation of one electroplax. Dahlgren has 

 shown that each electroplax probably arises from the union of all the 

 muscle-fibers in one mvotome. It was in the midst of these researches 



