DEVELOPMENT OF GALLUS 



219 



the hepatic portal vein, and the ductus venosus becomes the 

 hepatic veins and the base of the inferior vena cava. 



The allantois is supplied with blood by the umbilical 

 arteries (branches from the artery to the hind leg), and drained 

 by the umbilical veins. These run in the side wall of the 

 abdominal cavity and correspond to the lateral abdominal 

 veins of the dogfish. At first they run into the ductus Cuvieri 

 of their side, but later the right umbilical vein is reduced and 



Fig. 104. — Longitudinal section through an embryo showing the develop- 

 ment of the metanephros. 



(Actually, this section is of a mammal, not a bird, but the difference is 

 immaterial.) The ureter arises as an outgrowth from the Wolffian duct. 

 ce, ccelomic epithelium ; m, myotomes ; me, metanephrogenous tissue ; 

 mt, mesonephric tubules ; u, ureter ; Wd, Wolffian duct. 



the left one runs into the ductus venosus. At all events, the 

 blood from the allantois, where it has been oxygenated, runs 

 into the right auricle of the heart when the latter becomes 

 subdivided by interauricular and interventricular septa. The 

 left auricle receives the pulmonary veins. The lungs are, how- 

 ever, not functional, and by the breaking down of the septum 

 between the auricles, part of the blood from the allantois is 

 able to get from the right to the left auricle, and so to the left 



