68 



SCIENCE 



[N. S. Vol. XLV. No. 1151 



in her examination of several Gymnotid fishes 

 was unable to find electric tissues. She found 

 that 



in or between the first and second muscular units 

 of the ventral portion of the great lateral muscles, 

 there was a slight degeneration of parts of the 

 muscles. The larger units had been reduced to 

 two minute oval muscles embedded in either 

 strands of cartilage, or strands of cartilage and 

 fat, and occupied parts of two triangular spaces, 

 one on each side of the median septum just above 

 the (muscle) unit which controls the anal fin. No 

 plates, special nerve fibers, or nerve endings were 

 seen. 



In my examination of the specimen which 

 had been collected by Professor Dahlgren some 

 years ago, I noticed that when the fish was 

 scaled a portion of the body appeared almost 

 translucent. The location of this part corre- 

 sponds exactly to the location described by 

 Miss Lowrey where " slight degeneration of 

 parts of the muscles " had taken place. Sec- 

 tions were made of this portion of the body, 

 and a study of these has shown beyond all 

 doubt that the portion of the body in question 

 is composed of electric tissue. Not only were 

 the characteristic electroplaxes found, but also 

 the special electric nerve fibers and blood- 

 vessels supplying them. 



The fish used for this study measured ap- 

 proximately 31 cm. in length. The body is 

 more or less filiform, tapering to an extremely 

 finely pointed tail. The head is flattened 

 dorsally and the upper lip projects slightly 

 over the lower lip. The gill opening is rather 

 small with a dusky spot just above it. The 

 vent opens just behind the throat. The dorsal 

 fin is entirely lacking, while the ventral fin ex- 

 tends from the tip of the finely pointed tail 

 to a position just posterior to the vent open- 

 ing. The fin is controlled by a muscle unit 

 lying just dorsal to it. The electric organs 

 extend from the tip of the tail forward, fol- 

 lowing along the entire length of the ventral 

 fin and lying dorsal to the muscle unit con- 

 trolling the fin. There are two such organs, 

 one on each side of the body, each tapering 

 more or less at the cephalad and caudad ends, 

 thus giving the organs the form of much- 

 elongated spindles. In cross-section these 



electric areas appear triangular in shape and 

 are separated by the median septum. 



The electric spindles are divided into five 

 longitudinal tiers by horizontal sheets of con- 

 nective tissue running the entire length of the 

 organ. In these tiers the electroplaxes are ar- 

 ranged perpendicular to the septa in com- 

 partments boimded by the electrolemma and 

 embedded in the " electric jelly." These com- 

 partments, with the electroplaxes lying in 

 about the middle, are relatively large, with the 

 result that the electroplaxes are rather widely 

 separated. Since the strength of the electric 

 current produced is proportional to the num- 

 ber of electroplaxes, it is safe to assume that 

 the electric current produced by 0. carapus 

 must be extremely weak, if it is at all per- 

 ceptible. 



The electroplaxes are plainly seen in any 

 section taken through the electric organ. 

 They are more or less square or oblong in 

 shape, with irregular projections (papilte) on 

 the cephalad and caudad sides. These papillse 

 are usually longer on the caudad sides. Nu- 

 merous oval nuclei are arranged peripherally 

 and no cell walls are present. The core of the 

 electroplax is homogeneous in appearance. 

 The nerves and blood-vessels always approach 

 the caudad side of the plates, a condition which 

 is similar to that found in the electric eel and 

 other Gymnotids. 



It is thus evident that the tissue which Miss 

 LoviTey has described as degenerated muscle 

 units is really an electric organ. Her men- 

 tion of "strands of cartilage" being inter- 

 mingled with the degenerated muscle leads me 

 to believe that she has seen the electroplaxes 

 and interpreted them as being cartilage. They 

 are usually of a homogeneous, hyaline appear- 

 ance and with their numerous nuclei might 

 present a cartilaginous appearance. Yet their 

 form is that so characteristic of electric plates 

 that one can not overlook them. 



Another of the Gymnotids which Miss 

 Lowrey has examined and reported to possess 

 no electric organs is Eigenmannia virescens. 

 In the posthmnous work of Sachs (1881) on 

 Gymnotus electricus, some of his field notes 

 are published which describe and figure por- 



