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KAMAKICHI KLSHINOUYE : 
line over tlie cranium. In the Plecostei each myotome faithfully follows the 
course of the neural and haemal processes to their ends, at the median long¬ 
itudinal plane, not separating from them on the way, as is found in some 
teleostean fishes. Each myotome is bent in a zigzag line on the surface of 
the body, and may be separated into four parts, right, left, dorsal or epaxial, 
and ventral or hypaxial. The two lateral halves of the myotome are well 
separated by a thick membrane, aponeurosis, spun on the axial skeleton and 
its processes, and by the abdominal cavity. The membrane is very thick 
in the Plecostei. The dorsal and ventral portions are separated by a 
membrane of connective-tissue, connecting intermuscular bones, tendons, and 
ligaments. 
In the Teleostei muscle-fibres are generally well discernible from outside 
even in the last myotome (except in the genus Sarcla ) ; but in the Plecostei 
many caudal myotomes are changed to tendons at the posterior, external surface 
(fig, 3). Therefore the extremity of the caudal portion looks bluish, when the 
skin is removed. In the Plecostei nearly eight last myotomes seem to be 
fused into one. In Auxis the tendon of the last myotome is enormously 
elongated anteriorly, reaching far beyond the anus, to about the middle of the 
17th myotome (fig. 2). 
The muscular system, as may Ixi supposed from other structures, is well 
developed and much complicated in the Plecostei and allied fishes. The course 
of the myotome runs at its external surface from the dorsal median line sharply 
backward, then gently forward, and gently a little backward to the lateral 
median hue ; in the ventral half slightly forward, then, gently backward, and 
lastly sharply forward (fig. 3). The backward bend at the lateral median 
line is noteworthy in these fishes, in more primitive fishes the bend is not 
found at all. The bend is sharper in the anterior portion than in the posterior 
portion of the body. Indeed the zigzag course at the surface becomes more sharply 
bent as the position of the fish advances higher, and at the same time the conical 
forward outgrowth of the myotome is more elongated. The epaxial conical 
outgrowth is longer than the hypaxial, and is much more reduced in thickness. 
Therefore we find many concentric circles of myotomes in the cross-section of the 
lateral muscle, 3 or 4 in the Scombridae, about .10 in the Cybiidae, and 10- 
1G in the Plecostei (figs. 16-19). The backward bend of myotomes in the 
