THE GYMNOTID EELS OF TROPICAL AMERICA. 167 



center of the animal just below the lateralis inferior muscles and above the ventralis 

 muscles. In cross-section each half is roughly trapezoidal and about the size of 

 the muscle lateralis inferior. Macroscopically these two masses resemble electric 

 tissue. Their histological structure is to be discussed in another paper. 



Two other much smaller bundles of tissue, which did not seem to be muscles, 

 were found between the muscles ventralis and imus near the median line, not only 

 in Sternarchus alhifrons and Sternarchus Jiasemani, but also in Gymnotus carapo 

 (Linnaeus) and Adontosternarchus sachsi (Peters). 



These bundles were not so clearly defined as the first mentioned organs, and 

 may be nothing more than muscle fibers. See Plate XIX, Fig. 20. 



Food of the GYMNOTiDiE. 



References to the food of this group of fishes are few. Specific records were 

 found only for the electric eel. Kaup, in 1856, made a general statement concern- 

 ing the probable food of the fishes of the genus Rhamphichthys and from time to 

 time statements have been made concerning the food of the electric eel. Schles- 

 inger has recently speculated on the probable food of this group. His speculations 

 are based on the similarity of species of the Gymnotidce and the Mormyridce. 



Since large numbers of specimens of several species were available, a study 

 of the contents of their stomachs was undertaken. The large number of specimens 

 permits a detailed study of the food of Gymnotus carapo, Sternopygus macrurus, 

 Eigenmannia virescens and Eigenmannia macrops. The data for the other species 

 are rather incomplete. The stomach-contents were washed into Petri dishes with 

 alcohol. All of the large pieces were picked out and identified. The residue was 

 then taken up with a pipette and examined under the microscope on an ordinary 

 glass-slide, on which four pieces of glass had been cemented to form an alley a 

 little narrower than the field of the microscope. The results of the examinations 

 are tabulated for each species. In several of the tables the terms, "Insect debris," 

 "Vegetable debris," occur. No attempt was made to identify the vegetable matter. 

 The "insect debris" is a mass of parts of insects which could not be identified 

 with certainty. On the whole the stomachs were found either quite empty or 

 containing a large mass of food, little, if at all, mangled. Only a few of the stomachs 

 contained partly digested food. Examination of the intestines showed digestion 

 to be quite complete, for chitinous parts of insects and fragments of the calcareous 

 portions of macro-crustacea were the only undigested material found among the 

 otherwise soft intestinal contents. 



Gymnotus carapo Linnaeus. 



Snout short, heavy and blunt; conical teeth in both jaws; mouth large; 

 size, not exceeding 500 mm. 



