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PHYLUM CHORDAtA 1 CLASS PISCES — FISHES 



CJ/ 



The ventral aorta gives off, on each side, four afferent 



branchial vessels to the gills. 

 Thence the blood is collected by 

 four efferent trunks, which unite 

 on each side in an epibranchial 

 artery. The two epibranchials 

 are united posteriorly to form 

 the dorsal aorta, while anteriorly 

 they give off the carotids, which 

 are united by a transverse vessel 

 closing the " cephalic circle." 



Blood enters the sinus venosus 

 by two vertical precaval veins, 

 and by hepatics from the liver. 

 Each precaval vein is formed from 

 an anterior cardinal from the 

 head and a posterior cardinal 

 from the body. The posterior 

 cardinals extend along the kid- 

 neys, and are continuous with 

 the caudal vein, but the middle 

 part of the left cardinal is 

 obliterated. The circulation of 

 the blood seems to be helped, 

 in some fishes at least, by the 

 respiratory movements and by 

 the muscular contractions in 

 swimming. 



Excretory system. — The kid- 

 neys are very long bodies, ex- 

 tending above the swim-bladder 

 under the vertebral column. The 

 largest parts lie just in front of 

 and just behind the swim- 

 bladder. From the posterior 

 part an unpaired ureter extends 

 to the urinary aperture, before 

 reaching which it gives off a 

 small bilobed bladder. The 

 ; the functional kidney is a 



Fig. 358. — Diagram of 

 Teleostean circulation. — 

 After Nuhn. 



A ., Auricle ; V., ventricle ; b.a., 

 bulbus arteriosus ; v.a., ventral 

 aorta ; a.br., afferent branch- 

 ials ; e.br., efferent branchials ; 

 c.c, cephalic circle ; e., caro- 

 tids ; A .C.V., anterior cardinal 

 veins; P.CA^., posterior car- 

 dinal veins ; d.c, ductus 

 Cuvieri ; d.a., dorsal aorta ; 

 C.V., caudal vein ; c.a., caudal 

 artery ; A'., kidney. 



pronephros degenerates 

 mesonephros. 



