FKiriiK 2r, 



2") Transverse section of posterior end of :i 20 mm. cat embryo (series 241, 

 slide XXX. section 4), X 75 — showing extraintimal replacement of left supra car- 

 dinal vein (o9) by ascending lumbar rctroaortic lymphatic channel (TO). 



1 Sympathetic nerve. 



7 Aorta. 



58 Ureters. 



")9 Left supracardinal vein. 



60 Right supracardinal \('in. 



62 l']nd gut. 



63 N'eiitral division ol' cloaca luriiiaiy bladder). 

 (U Wolfiian duels. 



65 Metanephros. 



(id I'mbilical arterie.'^. 



67 Kiglit i)()8tcai-dinal vein. 



6S Left i)ostcardinal vein. 



7(i licl roaoi'tic supi'acardinnl iymi)li:i1 ic trunks. 



