. The chordates. Chordata. I 10 Comparative Morphology of Chordates Btto. discharge its powerful electric batteries. The fish is the ''electric eel," Electrophorus (or Gymnotus), a teleost. The electric organs are bulky paired masses of peculiar tissue occupying most of the ventral region of the very long tail (Fig. 339). The corresponding region in other fishes is occupied by the hypaxial divisions of the caudal myomeres. Another formidable fish is the electric ray, Torpedo, an elasmo- branch commonly found in the tropical and temperate waters of the Atlantic and occasionally elsewhere (
. The chordates. Chordata. I 10 Comparative Morphology of Chordates Btto. discharge its powerful electric batteries. The fish is the ''electric eel," Electrophorus (or Gymnotus), a teleost. The electric organs are bulky paired masses of peculiar tissue occupying most of the ventral region of the very long tail (Fig. 339). The corresponding region in other fishes is occupied by the hypaxial divisions of the caudal myomeres. Another formidable fish is the electric ray, Torpedo, an elasmo- branch commonly found in the tropical and temperate waters of the Atlantic and occasionally elsewhere (Fig. 339). It is a large fish, in extreme cases attaining a length of 5 feet and a weight of 200 pounds. The electric organs consist of a pair of large masses of electric tissue, each situated between the gill-chambers and the musculature of the pectoral fin of one side, and filling the entire space between dorsal skin and ventral skin. Malapterurus, a fresh-water catfish (Family Siluridae) of tropical Africa, is another electrically potent teleost. Its electric tissue is disposed as a sub- cutaneous layer (, between skin and body-muscle) investing the greater part of the body but thickest in the middle region of the trunk. In several other groups of fishes, relatively weak electric organs are present. The "stargazer" (Astro- scopus), an Atlantic teleost having eyes directed up- ward, possesses a pair of electric organs situated dorsally, each close behind an eye. Members of the teleostean Family Mormyridae, African fresh-water fishes, have electric organs in the tail. Among elasmobranchs, some of the common skates have weak electric organs in the anterior region of the tail. The structural unit of an electric organ, wher- ever situated, is an exceedingly thin plate of proto- plasm containing numerous nuclei, but not subdivided by cell-walls. The internal structure of this electroplax is too complex to admit of brief description (Fig. 340). Large numbers of these
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