FIGURE 25 



25 Transverse section of posterior end of a 20 mm. cat embryo (series 241, 

 slide XXX, section 4), X 75 showing cxtraintimal replacement of left supra car- 

 dinal vein (59) by ascending lumbar retroaortic lymphatic channel (76). 



1 Sympathetic nerve. 



7 Aorta. 



58 Ureters. 



59 Left supracardinal vein. 



60 Right supracardinal vein. 



62 End gut. 



63 Ventral division of cloaca (urinary bladder). 



64 Wolffian ducts. 



65 Metanephros. 



66 Umbilical arteries. 



67 Right postcardinal vein. 



68 Left postcardinal vein. 



76 Retroaortic supracardinal lymphatic trunks. 



