368 KAMAKICm KISHESfOUYE: 



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 obhquely 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 «ivery 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 tlae 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 cukineaus 

 veins, are found on each side of the body, on the epaxial and hypaxial sides 

 of the lateral median Hne. These two veins rim almost parallel, and quite near 

 each other. They run deep into the myotome of the fourth vertebra, at the 

 hind noargin 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 iinited 

 by a transversa commissure in tlie caudal portion. This ti-ansverse commissure 

 of the cutaneous vein is found in all the forms of the Thunnidae. Segmental 

 veins, both cutaneous and the veiiebral, are found in every myotome. 



In Paruthunnus (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 jjins the right Cuvierian duct after uniting with a short 

 renal vein. The caudal vein is very slender as in the genus Thunnm, and 



