238 



THE MESODERMAL DERIVATIVES 



Dorsal oorto 



Anterior cardinal vein (jugular) 

 I- 



Internal carotid ortery 



Left vitelline 

 vein 



Right vitelline vein 



Sinus venosus 



External carotid artery 

 Ventral aorto 



Bulbus arteriosus 

 Ventricle 



Dorsal aorta 



Pulmonary vein 

 Pulmo-cutanfous or 



r 



Anterior cardinal vein 

 Ductus cuvieri (jugular) 



Cutaneous 



artery / 



Pulmonary artery 

 Posterior vena cava 



Hepatic veiri 



External carotid 

 Ventral aorta 

 Bulbus arteriosus 



Ventricle 



Sinus venosus 



Right ouricle 



Blood vascular system of the developing frog embryo. (Top) Early embryo, 

 from the right side. {Bottom) Late frog embryo, from the right side. 



then must pass through the filaments of the internal gills until the 

 lung circulation develops. These gills degenerate at the time of meta- 

 morphosis. 



The paired dorsal aortae extend into the head and the aortic arches 

 of the first pair of branchial arches (visceral arch III), after the loss 

 of branchial respiration, remain to carry blood into the head from 

 the heart. These become the large anterior or internal carotids, orig- 



