372 KAMAKICHI KISHraOUYE : 



hepatic veins la-e divided very finely and run quite near the external surface 

 of the liver. In Parcdhunnns venules of the hepatic veins on the external 

 surface of the hver are rather short and sparce, while in Neothunnus venules 

 of the hepatic veins ai'e few, large and are not found at the external sui-faee 

 of the hver. In immatiu-e forms of our common tiumy venules on the sm-face 

 of the Hver ai"e short, i-emarkably shoiixjr tLan in the adult. In the Katsuwonidae 

 neither the plexus nor the parallel venules among the viscera nor those ou 

 the external sru'face of the liver are found. In Anxis, however, black dendritic 

 figm-es of the hepatic veins are noteworthy on the external surface of the hver. 

 In Eidhynn'us and Auxis the right lobe of the hver is elongated, and hepatic 

 portal veins from the pyloric coeca run in many transverse canals to the lobe. 



Heart. The heart hes just before the pericai'do- peritoneal septum, in a 

 more or less conical space, enclosed and protected by the lower pharj-ngeals, 

 clavicles, and pelvic girdle. The organ consists of a sinus venosus, aiuricle, 

 venti'icle, and bulbus arteriosus. Tlie sinus venesus is thin-walled and spacious, 

 formed by the union of the Cuvierian ducts below the oesophagus. The sinous 

 communicates with the auricle by a round opening. The auricle is a more or 

 less flattened sac with a tiiangular outhne, covering the dorsal anterior face 

 of the ventricle. The inner side of its wall is reticulated with muscle bundles. 

 The ventricle is firm, thick walled, more or less teti'ahedral in shape, with an 

 anterior vertex, ventral edge, and posterior base. In tlio anterior dorsal fat« 

 the ventricle is connected with the preceding cluimbers. Thus here the com'se 

 of blood-circulation is changed. The posterior face or the base is flat or rather 

 a little concave. The bulbus arteriosus is a laterally compressed sac, ovoidal 

 in form, with a well developed muscular wall. The sinu-ventrieular orifice is 

 eUiptical with two large pocket-shaped valves, while the auricuh-ventiicular 

 orifice is roundish, guarded with four hood-hke valves. The size of the heart 

 is remarkably large in the Plecostei as it projiels more blood than in the 

 Teleostei. The form of the heart is diflerent in the Plecostei, the base of the 

 ventricle is ueai'ly vertical in the order, while in the Scombridae and Cybiidae 

 it is obUque. 



Ai-terial system. The l)ulbus aiieriosus gradually pixsses to the short 

 ventral aoita M^hich gives off foiu: pairs of afleront Ijraudusil arteries. Tlie 

 aeriated blood in the gill-arches is mostlv can-ied dorsjilwards to the efferent 



