4 4 



Fig. 17 Transverse section of the same embryo at level indicated in pre- 

 ceding figure, to show the communication between the umbilical and omphalo- 

 mescnteric veins. Slide, 4, row 4, section 6, X 300. Reduced j. 



1 Aorta 5 Juxta-neural vessel 



2 Dorsal segmental artery 6 Somite 4 



3 Omphalomesenteric vein 7 Coelom 



4 Umbilical vein S Section of vessel of cardinal position 



72 



