330 PROCEEDINGS OF SECTION D. 



the more or less sinuous condition of the oesophagus at the time 

 of fixing ; sometimes, as seen in fig. 5, the oesophagus is practically 

 straight till it reaches the cardia at 0.41 mm. from the anterior tip, 

 while in the specimen in which the extreme position of 0.86 mm. 

 from the anterior end was reached, the oesophagus is much more 

 sinuous. Though sometimes situated at the termination of the 

 oesophagus, the cardia is at other times slightly in front of the 

 •entrance of the intestine. 



As a rule it is easy, unless hidden by the vagina, to detect the 

 exact junction because of the muscular walls, the cuticular lining 

 and, therefore, sharply marked lumen of the oesophagus and cardia 

 and the slightly wider non-muscular intestine (figs. 5, 6, 7, 8, 32 and 

 34), with irregular indefinite lumen and usually much darker walls. 

 The walls of the cardia are more muscular than those of the 

 remainder of the oesophagus, and the lumen not much greater. 



The chyle intestine varies about 0.046 mm. in diameter, its 

 lumen being in parts nearly obliterated. At about 0.207 mm. 

 from the anai opening, where it passes into the rectum, the 

 posterior end of the chyle intestine is suddenly constricted to 

 about one-third its previous diameter. 



The rectum (fig. 8) is a much swollen flask or pear-shaped 

 structure, its total length being 0.2 mm., and its maximum diameter 

 0.082 mm. The lining of the rectum is chitinous, and it contains 

 a considerable quantity of granular material. 



Nearly 0.2 mm. in front of the junction of the ch^le intestine 

 and the rectum there begins an irregular group of cells {see fig. 8), 

 which extends back to slightly behind this plane, and, doubtless, 

 comparable to those found in many other nematodes, though 

 usually less numerous than in this form, and variously described 

 in other forms as ganglion cells, or, more generally, as unicellular 

 glands. They lie in 0. gibsoni chiefly on the ventral surface, though 

 they extend half-way up the sides of the body, being attached to 

 the body wall. The granular material in the rectum has a similar 

 appearance to the content of the cells now under consideration. 

 Whether these cells are the exact equivalent of the three large 

 pear-shaped cells described by various authors (quoted by Looss 

 in the " Sclerostomes of Horses and Donkeys," in the report of 

 the Egyptian School of Medicine, Cairo, 1901, p. 58) is uncertain, 

 though probable. Their large number in this form makes one 

 hopeful that a further study of them may elucidate their morpho- 

 logical and physiological character — but as only one of the female 

 tails we have obtained is of good histological preservation, and as 

 so far the tail of the female has not been found, or at least recorded, 

 by other observers, we do not wish to use it for section purposes, 

 at all events at present. 



Surrounding the body at the level of the anal opening is a 

 muscle band, the fibres of which spread dorsally in a fan-like 

 manner, very similar to that found in other nematodes in a com- 

 parable position. 



