302 



COMPARATIVE ANATOMY 



existence (Anamnia), making use of its branchial vessels for par- 

 poses of respiration, the entire allantois, in the case of the Am- 



FIG. 242. DIAGRAM or THE EMBRYONIC VASCULAR SYSTEM. 

 (The portal systems are not shown. ) 



A, A, dorsal aorta ; RA, RA, right and left roots of the aorta, which arise from 

 the branchial vessels, Ab, by means of the collecting trunks, S, S 1 ; c, c 1 , 

 the carotids; Sb, subclavian artery; KL, gill-clefts ; Si, sinus venosus ; A, 

 atrium ; V, ventricle ; B, truncus arteriosus ; Vm, vitelline veins ; Am, 

 vitelline arteries ; Ic, Ic, common iliac arteries ; E, E, external iliac arteries ; 

 All, allantoic (hypogastric) arteries; Acd, caudal artery; VC, HC, anterior 

 and posterior cardinal veins ; Sb 1 , subclavian vein ; D, precaval veins (ductus 

 Cuvierii), into which the anterior and posterior cardinals open. 



phibia, giving rise to the bladder. In the Amniota, which from 

 the first breathe by means of lungs, a modification and reduction of 



