FIG. 68. TRANSVERSE SECTION OF AN EMBRYO OF THE FOURTH 

 DAY, PASSING THROUGH THE ANTERIOR PART OF THE LUNG RUDI- 

 MENTS. (After Duval.) 



Am, amnion. Ao, aorta. BP, bud of lung. 2 and (?3, heart. CC, Cuvier- 

 ian duct. Cam, amniotic cavity. CO, chorion. I A, fore-gut. Vva, anterior 

 branch of vitelline vein. VJ, wall of umbilical stalk. VM, mesoblast of peri- 

 cardium. 



208 



