40 



cells of the glandular epithelium of the tubules are cubical or columnar and 

 certain of them are longer than others and project into the lumen making the 

 inner surface of the tubule very irregular. The large round nucleus lies at the 

 base of the cell and the protoplasm at the distal end of the cell is granular and 

 often vacuolated. The epithelium is supported by a connective tissue frame work 

 which carries the veins and arteries. The secretion of the liver is proteolytic. 



The hepatic ducts are simple , thin-walled , muscular tubes lying side by side 

 and leading from the liver to the pancreas. The lumen of each duct is continuous 

 with those of the corresponding lobes of the liver and of the pancreas. 



The pancreas is a whitish, slightly lobulated gland surrounded by the 

 nephridial sac. As a whole it is U-shaped. The two arms begin at the points 

 where the hepatic ducts enter the ventral end of the nephridial sac and pass 

 backward, one on each side of the intestine. They unite behind it just before 

 the duct enters the caecum. The dorsal part of the pancreas Ues between , and 

 is partially adherent to, the two ventral lobes of the caecum. The wall of the 

 pancreas separates the lumina of the pancreas (the hepatico-pancreatic duct) and 

 of the nephridium ' and contains numerous evaginations from both cavities. The 

 external surface of the gland is covered by a palisadal epithelium which is the 

 reflected epithelium of the nephridal cavity. The nuclei of the cells of this epithelium 

 are arranged in a regular layer near the outer ends of the cells. The epithelium 

 forming the walls of the tubules of the gland is pavemental or cubical. The 

 extract of the pancreas is proteolytic, amylolytic, and oleolytic but it is possible 

 that the proteolytic enzymes are derived from the liver for it is impracticable 

 to remove the hepatic secretion from the lumen of the pancreas. 



Palloise finds that the hepatico-pancreatic secretion is continous but is much 

 more copious during digestion. The fluid is acid , colorless to brown or yeUow , 

 is rich in proteids, contains a proteolytic ferment, amylase, lipase and erepsin. 

 Invertin is absent. 



The gut distal to the caecum passes obliquely downward to the lower 

 surface of the visceral mass and then passes forward some distance. It is usually 

 divided , for purposes of description , into two portions viz : the intestine which 

 is a short wide tube extending from the caecum to the lower surface of the 

 visceral mass, and the rectum which is a long conical tube attached to the 

 lower surface of the visceral mass. 



The intestine passes forward from the caecum between the caecal lobes, 

 and between the oesophagus on the right and the pancreas on the left. Then 

 it turns sharply downward , passing between the right and left lobes of 

 the pancreas and between the two arms of the V-shaped nephridial sinus 



