348 
KAMAKICHI KISHINOUYE: 
in two bands in bonitos and tunnies, and being inferior in taste to tlie ordinary 
muscles. In tlie 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 segmentary arteries along the intermuscular bones. Tlie 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 coloured, 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 tlie centre of the concentric circles in 
the cross-section of the lateral muscle. In tminies the blackish red portion does 
not reach the vertebral column in the epaxial portion, but in the hypaxial 
portion it always reaches. This is well marked in the posterior portion of the 
body. The blackish red portion is thin and flat at the anterior part of the body, 
it then becomes gradually thick, thickest at the posterior part of the precaudal 
region and then being compressed laterally moves towards the surface together 
with the centre of the concentric circles in the cross-section. The boundary of 
the “ chiai ” portion is quite distinct. In the process of curing, the curer 
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 lias a wide base for the insertion to the axial 
skeleton as the dorsal aorta which supplies blood to the “ chiai ” portion is more 
or less separated from the vertebral column by the development of the epihaemal 
process. In tliis family the posterior part of the superficial lateral muscle is 
not so dark as the deeper layer. Tliis is due to the fineness of the cutaneous 
artery in the posterior part. The shape and volume of the “ chiai ” portion 
vary in different species. In the Thunnidae, Thunnus orientalis has a com¬ 
paratively large voluminous dark red portion, but Neothnnnus macropterus lias 
a small quantity of the dark red portion. In the Katsuwonidae the quantity 
of dark red portion is comparatively large, especially in Auxis which has about 
one fourth of the lateral muscle dark 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 
