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lower surfaces of the liver. The upper vein entei's the liver with the oesophagus 

 and passes more directly through the liver so that it emerges on the lower 

 surface some distance in front of the exit of the oesophagus and hepatic ducts. 

 The hepatic vein , formed by the union of the upper and lower veins , passes 

 through the liver case and enters the anterior vena cava obliquely so that the 

 lower wall of the vein forms a valve. 



The blood from the doi'sal third of the liver is collected by a pair of veins 

 (2''*) which arise near its dorsal point and pass forward to the hepatic ducts with 

 which they enter the nephridial sac. One of these vessels is often small or absent 

 wiiile the other is corresi)ondingly large. Within the nephridial sac these veins 

 pass along the outer wall of the pancreas, receiving blood fr(.)m it, until near its 

 middle where they meet other veins. The right vein unites with the large, 

 median , genital vein (y^) which passes ^vith the genital aorta between the 

 stomach and caecum , receiving venous blood from the stomach and from the 

 inner wall of the caecum. It empties into the right arm of the nephridial sinus. 

 The left vein unites with a vessel from the caecal folds (5°) and with a vein 

 from the intestine and then passes out of the pancreas to the left arm of the 

 nephridial sinus. 



A pair of small veins (P) passes backward from the sides of the rectum 

 and enters the lower side of the nephridial sinus almost opposite the entrance of 

 the preceding vessels. 



Three or four small veins (4'-) from the systemic heart empty into the 

 nephridial sinus. 



The ventral lateral pallial vein , (6^) formed by the veins of one side of the 

 ventral portion of the mantle, runs backward parallel to and outside of the 

 supporting membrane of the gill. At the base of the gill it turns abruptly inward 

 and, after receiving two vessels from the gill and passing above the branchial 

 heart, enters the nephridial sinus. One (7') of the veins from the gill comes 

 from the nerve and muscle which lie within the gill , the other (8^) comes from 

 the center of the bi-anchial gland. The left mantle vein as it passes over the 

 branchial heart receives a ventral vein (9*) from the penis or external oviduct 

 and a dorsal vein from the vas deferens, spermatophoric gland, and spermato- 

 phoric sac or from the oviduct and oviducal gland. A vein (11') corresponding 

 to a branch of the anterior aorta arises from the venous plexus (9-) at the back 

 of the mantle and passes through the mantle in a canal with the fin nerve to 

 join the ventral mantle vein. 



The Nephridial Sinus. (V). The median portion of the V-shaped nephridial 

 sinus or precava receives the blood from the anterior vena cava and the ends 



