DEVELOPMENT OF FOURTH DAY 



ft /r ~~H3^ ) 



9 



525 



Fig. 308. 



A to F, Diagrams illustrating the formation of the omphalomesenteric and 

 umbilical veins, in the chick. A. At about fifty-eight hours. B. At about sixty- 

 five hours. Veins joined dorsal to the gut. C. At about seventy-five hours. 

 Veins again separate. D. At about eighty hours. Secondary union of veins around 

 the gut. E. At about one hundred hours. Definite arrangement of the vessels. F. 

 Relationship of liver vessels, c. Vena cava posterior (inferior) ; dC, ductus 



