THE HYPOMERE (LATERAL PLATE MESODERM) 



243 



sinuses which shortly become organized into a vessel. This vessel con- 

 nects with the hepatic vein through a new junction anterior to the 

 liver. The median vein remains as the posterior vena cava to receive 

 blood from the tail, which degenerates at metamorphosis, and from 

 the kidneys (several short renal veins). After metamorphosis there is 

 no remnant of this vessel posterior to the kidneys, since the tail dis- 

 appears. Thus the post-caval vein is composed of several elements: a 

 hepatic vein derived from the original left vitelline vein; a short por- 

 tion of the right posterior cardinal vein; the median channel derived 

 from the fused right and left posterior cardinal veins; and a short 

 new section just posterior to the hepatic section, which grows pos- 

 teriorly. 



The lateral pair of vessels on the outer margin of the mesonephros 

 brings blood from the hindlimbs (sciatic and femoral) by way of the 

 common iliac, and from the dorsal body wall (lumbar). These are 

 known as the renal portal veins and terminate in the mesonephroi. 



The pulmonary veins arise at about the 6 mm. body length stage as 

 posterior dorsal outgrowths of the sinus venosus to the lung buds. 



ANTERIOR CEREBRAUINTERNAL CAROTIO 



EFFERENT 

 BRANCHIAL ART 



eULBUS ARTERIOSUS 



LINGUAL'VISCERAL \ 



VISCERAL III: BRANCHIAL I 



VISCERAL IV: BRANCHIALII 



VISCERAL V> BRANCHIAL III 



PUL. CUT. ARTERX^ 



CUTANEOUS ARTERY /« j i gLOMuS 



PULMONARY ARTERY 



VISCERAL Vl -BRANCHIAL IV 



SYSTEMIC TRUNK' 

 DESCENDING AORTA 



Blood vascular system of the frog tadpole — (Continued). Arterial system, 



ventral view. 



