452, MR. C. H. O DONOGHUE ON THE 
This sinus is partially divided into two chambers by an incom- 
plete vertical septum formed of interlacing trabecule. It passes 
through the pericardio-peritoneal septum and opens into the 
sinus venosus, however, by two small circular apertures, one 
on either side of the middle line, by means of which all the 
blood brought to the liver by the hepatic-portal vein and the 
hepatic arteries is returned to the heart. 
B. THe Renat Porta VEINs. 
1. The Caudal Vein (Parker) [Pl. I., C.] originates far back in 
the tail and runs forwards in the hemal canal ventrally to the 
caudal artery to a point just posterior and dorsal to the anus. 
Here it leaves the vertebral column and divides into two large 
equisized branches, the renal-portal veins. It receives numerous 
small branches from the myotomes of the tail. 
2. The Renal Portal Vein (Parker) [ Pl. I., R.P.] starts from 
the bifureation of the caudal vein and passes forward along the 
dorsal and dorso-lateral edge of the kidney, to which it sends 
numerous afferent renal branches. It gradually diminishes in 
calibre, and dies away towards the anterior extremity of the 
eaudal mesonephros at about the level of the front end of the 
vesicula seminalis in male. ‘The two renal-portal veins are 
completely separated in the middle line, and do not communicate 
directly with the posterior cardinal sinus. 
2.1. The Posterior Oviducal Veins (Parker) are small veins 
from the dorso-lateral wall of the posterior portion of the oviduct, 
and open into the renal portal vein. 
2. ii. The Posterior Parietal Veins (p.-spinal veins, Parker) 
arise from the myotomes of the region of the body along the 
side of the kidney, and open into the renal portal vein on its 
dorsal side. 
VII. Tur Coronary Verns (Text-fig. 4). 
The Coronary Veins are situated one on each side of the heart. 
Each of them is formed at the posterior end of the furrow 
separating auricle and ventricle, and enters the sinus venosus 
just behind the corresponding flap of the sinu-auricular valve. 
The posterior smaller vein collects the blood from the caudal end 
of the ventricle, while the remaining one collects blood from the 
anterior part of the ventricle, and, after receiving a well-marked 
tributary from the conus arteriosus, runs backwards in the 
groove between auricle and ventricle. - Small factors from the 
auricle probably join the coronary veins, but are difficult of 
injection. 
VIII. Tue Ducrus Cuvier. 
The Ductus Cuvieri (Parker) [Pls. I. & IJ., D.C.] convey to 
the heart all the venous blood save that brought by the hepatic 
veins. Their anatomical relations in the adult have already been 
briefly noted. The outer end forms a spout-like structure with an 
oval end projecting into the posterior cardinal sinus. Each passes 
