0^8 KAIIAKICHI KISHINOUYE: 



in two baiicTs in bonitos and tunnies, and being inferior in taste to the ordinary 

 muscles. In the Plecostei the ordinary flesh is remarkably reddish, as the 

 special superficial segmentary canals send a copious flow of blood into it (fig. 3). 

 The dark colour of the median superficial muscle is due to the rich supply of 

 blood from s^mentary arteries along the intermuscular bones. The darker 

 colour of the " chiai " portion is also due to the same cause, but from a 

 different source. 



In the Plecostei as the ordinary muscles are red colotu^ed, the median 

 superficial muscle as well as the deeply seated portion round the axial skeleton 

 are nearly blackish red as they receive more blood than the ordinary muscle. 

 The blackish red portion scarcely reaches the centre of the concentric circles in 

 the cross-section of the lateral muscle. In tunnies the blackish red portion does 

 not reach the vertebral colmnn in the epaxial portion, but in the hypaxial 

 p)i*tion it always reaches. This is weU marked in the posterior portion of the 

 body. The blackish red portion is tliin and flat at the anterior part of the body, 

 it then Ijecomes gi-adually thick, tliickest at the posterior part of the precaudal 

 r^on and then being compressed laterally moves towards the surface together 

 with the centi'e of the concentric circles in the cross-section. The boundary of 

 the " chiai " portion is quite distinct. In the process of curing, the eurer 

 observes that the " chiai " portion is liable to separate from the surrounding 

 portion. In the Katsuwonidae the epaxial portion also reaches the axial skeleton 

 (fig. 19), and the hypaxial portion has a wide base for the insertion to the axial 

 skeleton as the dorsal aoiia which supphes blood to the " chiai " portion is more 

 or less separated from the vertebral colimm by the development of the epihivemal 

 process. In this family the posteiior part of the superficial lateral muscle is 

 not so dark as the deeper layer. This is due to the fineness of the cutaneous 

 artery in the ^»sterior paii. The shape and voliune of the " chiai " portion 

 vary in different species. In the Thimnidae, Thunnus orientalis has a com- 

 paratively Lirge voluminous dark red portion, but Neothwmm macrapterus has 

 a small quantity of the dark red portion. In the Kiitsuwonidae the quantity 

 of dark red ^xirtion is comparatively huge, especially in Auxis which has about 

 one fom'th of the lateral muscle daxk coloured. In the " chiai " portion tendons 

 are well developed, especially in the epaxial portion and in the caudal portion 

 (fig. 2). In the Teleostei the most active part of the lateral muscle seems to 



