MUSEUM OF COMPARATIVE ZOOLOGY. 155 



from participating in the boundary of the lumen, which is now Hmited 

 by only three cells, one dorsal and two ventral. The cell, thus forced 

 back from the lumen, dwindles away, and is not replaced by another. 



A lumen bounded by three cells persists for some distance backward, 

 but finally another cell disappears and the lumen lies between two cells 

 (Fig. 49). I did not succeed in finding the exact spot where the dis- 

 appearance of the third cell takes place, and am hence unable to give the 

 details of the process. From this place posteriad all further change is 

 of degree and not of kind, since the intestine simply grows smaller, the 

 lumen all but disappears (Figs. 46-48), and finally the whole structure 

 vanishes (Fig. 9) shortly before the end of the body is reached. In no 

 case, either in entire prepai'ations or in sections, was I able to trace it 

 nearer than within a few millimeters of the posterior end of the body ; 

 and since it was entirely free at its termination, no clue was given as to 

 its relation to the terminal orifice of the body. Since this orifice is 

 clearly connected with the sexual organs, as will be demonstrated 

 later, it remains doubtful whether it is a cloacal opening, or whether 

 the end of the intestine is to be found elsewhere. Certain it is that 

 in the intestine we have a highly degenerate organ, so that from a 

 study of the adult alone no light can be gained as to its termination. 

 It is interesting to note that the oesophagus is intracellular, the intes- 

 tine however clearly intercellular. 



No mesenteries were found binding the intestine to the body wall, and 

 consequently its position varies in different individuals. It was more 

 often ventral than dorsal, and lateral than median. In the female 

 (Plate IV. Fig. 58), however, it extends directly through the middle of 

 the mass of nearly ripe eggs. 



The description of the structure of the alimentary canal already given 

 for the male, holds good for the female as well, except that the lengths 

 of the various parts are somewhat less than those of the male. The 

 anterior chamber is much smaller, and the parts contained in it more 

 compressed. 



Burger ('91, p. 643) described in general the four intestinal cells un- 

 der the somewhat inappropriate name of oesophageal cells. He failed 

 to recognize the cellular nature of the real oesophageal cell, since he 

 speaks only of the tube and of a fibrous envelope. He seems to have 

 entirely overlooked the loop in the tube, which probably existed in 

 sections between those represented in his Figures 22 and 23, and nat- 

 urally was able to give but little on histological structure. I do not 

 believe it is advantageous to speak, as he does, of the intestinal cells as 



