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oesophageal and inner buccal sinuses and entering the lower side of the pharynx 

 opens into the mouth at the tip of the tongue. 



The Oesophagus. The oesophagus extends from the pharynx through the skull, 

 the oesophageal nerve ring and the liver to the stomach. It passes directly 

 backward in the oesophageal sinus until it has passed under the cerebral ganglion, 

 then it turns slightly upward and passes thru the fascia that closes the large 

 foramen of the skull. This fascia separates the liver from the oesophageal nerve 

 ring , covers the visceral ganglion , and closes the dorsal end of the inner buccal 

 sinus. Having left the head , the oesophagus passes obliquely upward and back- 

 ward thru a very deep groove (apparently a canal) in the liver to its upper 

 surface. It continues backward in a shallow groove on this surface until some 

 distance beyond the middle of the liver. At this point it passes obliciuely downward 

 thru the liver and emerges on its lower surface between the hepatic ducts. The 

 oesophagus after leaving the liver , passes between it and the nephridial sac, and 

 being deflected slightly to the light enters the ventral end of the stomach near 

 the middle of the visceral mass. The wall of the oesophagus is formed by a thick 

 outer layer of circular muscle fibres, a thin inner layer of longitudinal muscle 

 fibres and a columnar epithelium which secretes a thin chitinous cuticle. This 

 cuticle is continuous with that which covers the surface of the odontophore and 

 the inner sides of the palatine lobes and with the lining of the stomach. 



The Stomach. The stomach and caecum are oval muscular sacs w^hich lie 

 on the right and left side respectively and project into the coelom from its 

 ventral end. The nephridia and the branchial and systemic hearts are below 

 these organs ; the dorsal end of the liver is above them : and the gonad lies 

 above and behind them. The stomach and the caecum are very distensible and 

 may occupy only the ventral thii'd of the coelom or may extend nearly to its 

 dorsal end. 



The stomach is a thick-walled, muscular, oval sac, whose inner or left surface 

 is adherent to the inner surface of the caecum. Its wall is formed l)y five layers 

 viz. 1 ) the peritoneum , a sheet of ciliated pavement epithelium : 2) a thin outer 

 layer of oblique muscle fibres; 3) a thick middle layer of circular muscle fibres; 

 4) a thin inner sheet of oblique muscular fibres; o) a. palisadal epithelium that 

 secretes a chitinous cuticle which lines the stomach. There are no mucous or 

 other secretory glands in the walls of the stomach and oesophagus 



The Caecum. The caecum has a very thin wall. It is larger than the stomach 

 and is closely connected with it. The openings (which will be more fully 

 described below) connecting the caecum with the stomach , intestine , and liver 

 are close together at the ventral end of the caecum. They lie in the crest of a 



