-SEA-FISHERIES LABORATORY. 21 3 



stomach and the right and dorsal surface of the spleen. 

 It is a large thin-walled sac about one inch in diameter 

 in large plaice. It is not imbedded in the liver in any 

 way, and is attached to the latter organ by means of the 

 bile duct only. Its posterior wall is thickened by a little 

 nodular swelling. Its efferent duct leaves the anterior 

 and ventral surface, turns back and runs on the internal 

 surface of the right hepatic lobe partially imbedded in the 

 tissue of the latter. Three groups of hepatic ducts enter 

 it : one of these is situated near the proximal end of the 

 duct, the other two are placed about midway on its course 

 and enter it from opposite sides. Each is a group of three 

 or four ducts. The cystic duct is the portion of the whole 

 duct between the gall bladder and the opening of the first 

 hepatic duct, -the remaining portion is the common bile 

 duct. The walls of the bile duct are slightly iridescent, 

 the distal extremity is thick and swollen, but encloses a 

 very narrow lumen. It enters the duodenum between the 

 paired pyloric caeca. Its opening into the duodenum is 

 extremely small, and is very difficult to observe from the 

 interior of the latter. The bile is a transparent slightly 

 greenish fluid. The liver in the plaice, as in all other 

 vertebrates, has a double blood supply, receiving blood 

 from the veins of the intestine by the hepatic portal 

 channels and from the dorsal aorta via the coeliaco-mesen- 

 teric artery by the very small hepatic artery (A. hep. fig. 

 22). Of these sources the hepatic portal system of veins 

 is by far the most important, and the system of intra- 

 hepatic vessels containing venous blood is exceedingly 

 striking in sections of the organ. The liver is essentially 

 a tubular gland, but the hepatic tissue is disposed in 

 strings of cells in which as a rule the lumen or bile capil- 

 lary is only apparent from the radiate arrangement of the 

 hepatic cells in transverse section of the strings. Within 



