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KAM AK ICH! KISHINOUYE: 
The venous system of the Cybiidae (fig. 6) is nearly similar to that of the 
Scombridae ; but differs in the development of the renal portal system in the 
precaudal region, where some segmental veins running along neural processes 
and intermuscular bones are minutely divided in the kidneys. Nearly at the 
posterior end of the precaudal region the cardinal vein leaves the haemal canal 
and runs obliquely downward to clear some preceeding haemal arches and 
short haemal spines and passes through the kidney, receiving numerous venules 
there and taking a more or less ascending course rejoins the dorsal aorta in 
the haemal canal. The segmental vein is not found in every segment, but 
almost in every other segment, alternating with the segmental artery as in the 
Scombridae. 
In the Plecostei the venous system differs greatly from that of the Tele- 
ostei, as stated above, moreover there is a great variety in the system in 
different forms of the order. In the genus Thunnus, the most primitive type 
of the Plecostei, the cutaneous system is best developed, and the vertebral system 
is abortive, the posterior cardinal vein being wanting. A short, slender caudal 
vein is found in the place of the posterior cardinal vein. The caudal vein 
joins at the middle part to the transverse commissure of the cutaneous veins 
and thus communicates indirectly with the Cuverian ducts. A pair of cutaneous 
veins, are found on each side of the body, on the epaxial and hypaxial sides 
of the lateral median line. These two veins run almost parallel, and quite near 
each other. They run deep into the myotome of the fourth vertebra, at the 
hind margin of the myotome, and unite a little below the surface of the body. 
The confluent vessel runs obliquely anteriorly, passes under the proximal slender 
part of the third rib, and joins the Cuvierian duct of the respective side, after 
collecting many renal venules. The right and left cutaneous veins are united 
by a transverse commissure in the caudal portion. This transverse commissure 
of the cutaneous vein is found in all the forms of the Thunnidae. Segmental 
veins, both cutaneous and the vertebral, are found in every myotome. 
In Parathunnus (fig. 4) the cutaneous veins of both sides pass through the 
myotome of the sixth vertebra, and each uniting to a large vein running below 
the fifth rib, pour into a transvers canal behind the pharyngeal muscles. 
The transvers canal joins the right Cuvierian duct after uniting with a short 
renal vein. The caudal vein is very slender as in the gemrs Thunnus , and 
