422 EMBRYOLOGY OF THE LOWER VERTEBRATES en. 



the hind end of the heart. The two vitelline veins become connected 

 by a transverse anastomosis dorsal to the gut and just behind the 

 dorsal pancreatic rudiment (Fig. 195, B). The parts of the veins in 

 front of this anastomosis break up into a network in the substance of 

 the liver, and the two networks become continuous with one another 

 (Fig. 195, C). The two vitelline veins now form another anastomosis 



rail 



p.vc. 



loll 



roll 



LaZL 



p.vc 



I'n.. 195. Diagrams to illustrate the development of the ventral part of tin- venous 

 in in Lccerfit oyilis as seen from the ventral side. (After Hochstetter, 1892.) 



ab, abdominal vein; <!.<'. ilucl <>l ('uvii'i : </./. ilurtns venosns ; int. alimentary canal; Lull, left 

 :ill;intoir rate] /'. liver: /.-.,-. l.-lt vilelliin- vein ; /., jx.rlal vein ; /..<... posterior vena c;n .. 

 allant nt \ it.-lliii \.-in. 



\\nli on- i.iK.ilicr farther b;n-k and ventral to the alimentary canal 

 (Fig. 195, C). The rijjht vitelline vein becomes rctltK-cd and finally 

 nl.liici-atrd in tlic IVJK.II in iV.ni (.I'this ventral anastnnms is s<> that 

 i he wlnl; 1 ilood -stream j. asses forwards tn tin- level of the dorsal 

 anastoiiHJHM l.y 1li- p.-i-sist-enl lel't, \.-in ( Ki.ir. l ( .r, I), l.r.v). lu the 

 region anterior 1<> tin- drs;il anastiuinsiK tin- 1T|. \-in now diniinislics 

 in i/c and finally disappears, iirst in the region behind tin- hepatic 



