420 



COMPARATIVE ANATOMY 



Sff 



DOs 



Vnl 



FIG. 324. DIAGRAM OF THE VENOUS SYSTEM OF Amphioxns. 

 (After B. Zarnik.) 



DCd, DCs, right and left precaval ; Ds, intestinal sinus ; Gg, genital vessels ; 

 LI, heptic lacunae ; Lv, hepatic vein ; PI, parietal lacunae ; Qv 1 , Qv 1 , 

 transverse veins; Sv, vental aorta ("sinus venosus ") ; Vca, anterior 

 cardinal ; Vcd, caudal ; Vcp, posterior cardinal ; Vsi, subintestinal vein. 



extends into the caudal region as the post-anal gut. On the 

 disappearance of the latter, the posterior part of the subintestinal 



