CIRCULATORY SYSTEM. 



which passes both in and 



-PCX 



out under the operculum. 

 The gill filaments borne on 

 the four anterior branchial 

 arches are long triangular 

 processes, whose free ends 

 form a double row. As there 

 are no partitions between 

 the five gill clefts, the fila- 

 ments project freely into the 

 cavity covered by the oper- 

 culum. Along each arch and 

 filament there are blood 

 vessels, bringing the impure 

 blood, and removing it puri- 

 fied. On the internal surface 

 of the operculum lies a red 

 patch, the pseudobranch or 

 rudimentary hyoidean gill. 



The swim bladder lies 

 along the dorsal wall of the 

 abdomen; the duct which 

 originally connected it with 

 the gut has been closed. 

 The dorsal wall of the 

 bladder is so thin, that the 

 kidneys and vertebrae are 

 seen through it ; the ventral 

 wall is thick, and bears 

 anteriorly a large vascular 

 rete mirabile, which receives 

 blood from the mesenteric 

 artery and returns blood to 

 the portal vein. 



Circulatory System. 



The heart lies within a peri- 

 cardial chamber, separated by 

 a partition from the abdo- 

 minal cavity. The blood from 

 the body and liver enters 

 the heart by the sinus venosus, passes into the thin-walled 



FIG. 169. Diagram of 

 Teleostean circulation. (After 

 NUHN.) 



The venous system is dark. A., 

 auricle ; V., ventricle ; b.a., bulbus 

 arteriosus ; v.a., ventral aorta; a. fir., 

 afferent branchials ; e.br., efferent 

 branchials ; c-c., cephalic circle ; c., 

 carotids ; A.c.v., anterior cardinal veins ; 

 P.C.V., posterior cardinal veins; d.c., 

 ductus Cuvierii ; d.a., dorsal aorta ; c.v., 

 caudal vein ; c.a., caudal artery ; k., 

 kidney. 



