COMPARATIVE STUDY OF SCOMBROID FISHES. 
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lateral median line of the body, running to the deeper part of the body 
between the myotonies of the fourth and fifth vertebrae. The chief cutaneous 
segmental veins are united to the epaxial cutaneous vein, and sheets of 
vascular plexus surrounding the dark red portion of the lateral muscle are 
connected with the vein. The hypaxial cutaneous vein is remarkably short, 
slender, and- zigzag in its course, disappearing from the surface of the body 
just behind the postclavicle and before the myotome of the first vertebra. In 
the Katsmvouidae the hypaxial cutaneous vein always passes before and above 
the first rib. The posterior cardinal vein leaves the haemal canal from the 
fourteenth vertebra or a still more backward position. Anterior to that point 
the posterior cardinal vein is more or less separated from the dorsal aorta, 
receiving several short but comparatively large veins at both sides of the 
dorsal aorta, and these veins are formed from parallel venules of the vascular 
plexus in the haemal canal or “ kurochiai ” in Japanese. At the same point 
an inferior posterior branch joins the posterior cardinal vein. The branch is a 
slender renal vein as in Neothunnus. The cardinal vein and the dorsal aorta 
too are situated close to the lower side of the haemal canal, sending a thick 
rod of vascular plexus above, which fills up the broad canal. The kurochiai 
appears from the segment of the fifth vertebra in Katsuiuonus, from that of the 
sixth vertebra in Euthynnus yaito, from that of the ninth in Neothunnus , and 
tenth or twelfth in Auxis. In the latter genus the epaxial cutaneous vein 
passes between the two accessory cones of the lateral muscle (fig. 2). 
The visceral venous system of the Plecostei consists of some hepatic portal 
veins, hepatic veins, and genital veins. The chief difference from the Cybiidae 
and Scombridae lies in the genital veins, which directly join the Cuvierian 
ducts. In the Thunnidae the hepatic portal veins are more or less divided 
into plexuses or parallel venules before entering the liver. The plexus is most 
remarkably developed in Thunnus. In this genus the venules are interlaced 
with arterioles of the coeliac artery. Each plexus is as large as a fist, and is 
more or less conical. In another genus, Parathumus, only venules are found in 
the plexus, consequently the plexus is thin, elongated, and in the genus Neothunnus 
the plexus is not found at all, but instead of a single trunk, the hepatic 
portal veins are composed of several parallel venules. Concomitantly with the 
development of the peculiar plexus on the internal side of the liver, the 
