252 



DIPNOI 



Dipneumones pass directly, without breaking up into capillaries, to 

 the aorta, as in terrestrial vertebrates. In Ceratodus, but not in the 



-ptv. 



cv. 



FIG. -l-l-l. 



Diagram of the venous system of Ceratodus Forxteri, dorsal view. (After Spencer.) a , atrium ; 

 !>, anterior abdominal vein ; br, branchial vein ; c, con us; c.v, caudal vein ; h.p, hepatic portal 

 vein ; i.j, inferior jugnlar vein ; il, iliac vein ; A 4 , kidney ; I, liver ; l.c, lateral cutaneous vein ; 

 l.p.c, left posterior cardinal ; p, pulmonary vein ; pt.v, posterior vein from body-wall ; p.v, pelvic 

 vein ; r.p, renal portal vein ; r.p.c, right posterior cardinal ; <, subclavian vein sj, jugular 

 vein ; t, testis v ventricle ; v>c, vena cava. 



Dipneumones, the hyoidean hemibranch is a pseudobranch, receiving 

 blood only from the efferent system (Spencer, Parker, Figs 220-21). 

 Three chief points of interest are found in the venous system 

 (Figs. 222-4). Firstly, the pulmonary blood is returned directly to 

 the heart by a vein passing to the left side of the sinus venosus, as 



