422 



COMPARATIVE ANATOMY 



II 



Os 



-Cdv 



Fi<;. 3'26. DIAGRAM OK STACKS IN THE DEVELOPMENT OF THE VEINS IN ELASMO- 

 BRANCHS. (I XI after Rabl, XII after F. Hochstetter. ) 



Ca, C'p, anterior and posterior cardinal veins ; Cdv, caudal vein ; C7, region of 

 the cloaca ; DC, precaval vein or sinus ; D, D, vitelline veins ; H, sinus 

 venosus of heart ; J, subintestinal vein ; Jr. V, interrenal vein ; Lb, hepatic 

 veins ; Npf, renal portal system ; O, Od, left and right omphalo-mesenteric 

 veins ; She, subclavian vein; VP, hepatic portal vein ; Vpo, capillaries of the 

 hepatic portal system ; " :i , hepatic sinus ; f, cardinal sinus. 



the main trunk of the left omphalo-mesenteric vein breaks up into 

 hepatic capillaries, which again unite anteriorly, opening into the 

 proximal ends of both these veins. The latter thus give rise to 



