27 



very distinctly rounded off, forming an uneven lower 

 margin, which rests on a fibrous sheath consisting of 

 several layers, and which passes into the loose connective 

 tissue surrounding the digestive gland tubules. 



The thickness and extent of the tricuspid body is 

 variable, some portions of the stomach-wall being bare; 

 the latter is thrown into folds and pads, into which the 

 substance of the tricuspid body dips. In most parts this 

 substance is closely adherent to the gastric epithelium, in 

 other parts it is distinctly separated ; where it lies in 

 close contact with the epithelium the striated free border 

 of the latter is very evident. Where it is separated the 

 epithelium is seen to bear cilia which, at other places, 

 must be embedded in its substance. It stains slightly 

 with eosin. No obvious structure can be discerned in it 

 except that in favourable preparations, delicate striae, 

 parallel to the surface of the epithelium, and other striae 

 perpendicular to the surface may be seen, which seem to 

 indicate that it has been deposited round the cilia and in 

 laminae, perpendicular to the surface of the epithelium. 

 Where the tricuspid body is wanting the gastric epithelium 

 is composed of much shorter spindle cells than are found 

 elsewhere. The average length of the cells beneath the 

 tricuspid body is 0'08 mm., on the rest of the stomach- 

 wall 0'04 mm. 



The whole posterior part of the stomach contracts to 

 form the straight portion of the intestine (Al.c.3, fig. 3). 

 This extends downwards nearly in the axial line of the 

 proximal limb of the viscero-pedal mass. It is slightly 

 curved, the concavity being anterior. The diameter, the 

 average value is 1*25 mm., decreases from above down- 

 wards. At the lower end and on the anterior side, the 

 spiral portion of the intestine takes origin, below this there 

 is a short anteriorly directed caecum. 



