154 BULLETIN OF THE 



transverse sections at short intervals (Figs. 31-44). The general form 

 of the tube may also be seen in the optical section represented in 

 Figure 8. 



The oesophagus varies from 0.75 to 1.5 mm. in length, being from ^ 

 to ^0 of the total length of the worm. The loop which occurs near its 

 posterior termination measures from 50 to 100 /x in length, and from 20 

 to 30 fji in width. It lies nearly in the sagittal plane, and ventral to 

 the general course of the oesophageal tube. The absolute uniformity of 

 its occurrence and the normal appearance of the adjoining intestinal 

 cells, preclude the idea that this is an accidental fold. It must be 

 regarded as a normal yet very curious feature of the oesophagus. 



b. Intestine. 



The intestinal cells, which, as has been shown, are first encountered on 

 the oesophageal cell just behind the partition,, are four in number at 

 the point where the intestinal cavity is formed and the oesophagus 

 opens into it. These four however clearly constitute two pairs which 

 are unlike (Fig. 37). The contents of one pair is a coarsely granular 

 plasma, whereas that of the other pair is finer. The first remains un- 

 stained in hsematoxylin, but takes up enough hydrochloric acid car- 

 mine to give the plasma a reddish tinge. The reverse is true of the 

 other pair of cells. Occasionally the granules in the first pair of cells 

 become very coarse, and then appear like excretory secretions. As 

 already mentioned, there are no transverse partitions dividing the cell 

 (Fig. 52), although a very large number of nuclei are present, usually 

 several in each section (Fig. 39). Only two of the four cells are repre- 

 sented in Figure 52, which is a surface view. The difi'erences in the 

 character of the nuclei are well shown in the figure. 



The walls of the intestinal cells are very strong, perhaps even cuticu- 

 lar, since they remain intact long after the cell contents have been 

 completely macerated out. There is however, no special chitinous lin- 

 ing for the intestine, such as Burger has figured ('91, Taf. XXXVIII. 

 Figs. 25, 29). This appearance is probably due to the partly macer- 

 ated and detached memV)ranes of the adjacent cells. 



The portion of the intestine bounded by four cells is relatively short. 

 One of the finely granular cells ^ dwindles down to a point (Fig. 45) 

 and a new one takes its place. This pushes itself obliquely under the 

 adjacent coarsely granular cell on one side, so that the latter is excluded 



1 Owing to a break in the series figured, I am unable to state positively which 

 one of the original four is the first to disappear. 



