340 KAMAKICHI KISHINODYE : 



line over the crauium. lu the Plecostei each myotome faithfully follows the 

 course of the neural mid hasmal processes to their euds, at the inediau long- 

 itudiuid pliiue, not separating fi'om them ou the way, as is found in some 

 teleosteau fishes. Each myotome is bent iu a zigzag line ou the surface of 

 the Ixxly, and may be separated into fom* parts, right, left, dorsal or epaxial, 

 aud venti'al or hypaxial. The two lateral luxlves of the myotome are weU 

 separated by a thick membrane, aponem'osLs, spuu ou the axial skeleton and 

 its processes, and by the abdominal cavity. Tlie membrane is very thick 

 in the Plecostei. The doreal aud ventral portions ai'e separated liy a 

 membraue of connective-tissue, counecting intermuscular bones, tendons, and 

 ligaments. 



Iu the Teleostei miBcle-fibres ai'e generally weU discernible from outside 

 even iu the last myotome (except iu the genus Sarda) ; but in the Plecostei 

 many caudal myotomes are changed to tendous at the posteiior, esterutil sm'face 

 (fig, 3). Therefore the exti'emity of the caudal portion looks bluish, M-heu the 

 skin is removed. In the Plec stei uearly eight last myotomes seem to be 

 fused into one. In Auxis the tendon of the last myotome is enormously 

 elongated anteriorly, reaching fcir beyond the anus, to about the middle of the 

 17th myotome (fig. 2). 



The muscular system, as may Ixi supjwsed from other structures, is well 

 developed and much complicated iu the Plecostei aud allied fishes. The com-se 

 of the myotome runs at its external surface fi'om the doi"sal median line sharply 

 backward, then gently forward, aud gently a Httle backward to the lateral 

 median line; iu the venti'al half slightl3- forward, theu, gently backwai'd, jmd 

 kistly sharply forwai'd (fig. 3). The backward bend at the lateral mediixu 

 line is noteworthy in these fishes, in more primitive fishes the l)end is not 

 found at all. The bend is sharper iu the anterior portion than in the ixsterior 

 portion of the body. Indeed the zigzag coui-se at the surface becomes more sharply 

 bent as the iiosition of the fish advances higher, aud at the same time the corneal 

 forward outgrowth of the myotome is more elongattid. Tlie epaxial conical 

 outgi'owth is longer than the hypaxial, aud is much more reduced in thickness. 

 Therefore we find mimy concentric circles of myotomes in the civss-soction of the 

 lateral muscle, 3 or 4 in the Scombridae, about 10 in the Cybiidive, and 10- 

 16 iu the Plecostei (figs. 16-19). The backward bend of myotomes iu the 



