316 CRKSSWEfJi SHEAKEK. 



vegiou of the stomacli the wall is relatively thin in comparison 

 with that of the anterior part, and its cells on the ventral 

 side are fnrnished with very long, dense cilia. 



About the middle of the end of the third segment the 

 stomach contracts into a narrow mid-gut, which runs 

 through the generative region to widen somewhat in the 

 caudal region into a more or less straight hind-gut. The 

 lumen of the intestinal tract, from the stomach backwards, is 

 greatly reduced in size, and, in the contracted condition of 

 the animal, somewhat folded on itself. The character of its 

 ciliation is also different from that of the stomach. At the 

 point where the stomach passes into the mid-gut there is a 

 sort of valve formed by the thickening of the stomach-wall. 

 A similar valve is found at the point of union with the hind- 

 gut. The wall of the mid-gut is relatively the thinnest part 

 of the tract, and its cells are not of the marked yellow colour 

 of those of the stomach. The course of the mid-gut is 

 irregular, from its being slightly folded on itself. That of 

 the hind-gut is comparatively straight, but its lumen is 

 irregular and wavy in outline, due to the irregular thicken- 

 ing of the wall at different points on its course. Throughout 

 the generative segment the gut is- very closely confined 

 against the dorsal body-wall. The anus is dorsal. The cells 

 of the hind-gut are of a character quite different from those 

 of the other parts of the tract. They are quite irregular in 

 size, and extend into the lumen so as to make its outline very 

 broken, as if thrown into a number of convolutions. In no 

 part of the wall of the stomach or gut are any contractile 

 muscular fibres to be seen. In the body-cavity, ventral to 

 the anus, and close to the point where the gut joins the body- 

 wall to form the anus, there is usually present a conspicuous 

 cell on either side. The anus itself is an oblong, vertically 

 placed, T-shaped slit placed more towards the dorsal than the 

 ventral side of the animal. It is apparently kept closed b}- 

 some contractile fibres of the cuticle which function as a sort 

 of sphincter muscle. 



The digestive tract of Stratiodrilus agrees in all essen- 



