241 



in obtaining the head. As only one such specimen was col- 

 lected, the measurements are necessarily based on it and 

 do not indicate any range of variation. The head end is 

 bluntly rounded, and almost at once assumes a diameter of 

 '03 mm., reaching '04 at the level of the nerve-ring ('16 mm. 

 from the mouth). The increase in diameter is so gradual 

 that at 40 mm. from the mouth it is only '05 mm. Ultim- 

 ately the width reaches a maximum of '18 to '20 mm.. 

 Towards the posterior end it tapers to about '16 mm. (at 

 "6 mm. from the tip), then rather more quickly towards the 

 tail (fig. 8). At the level of the anus (which lies at '13 mm. 

 from the tip) the diameter is '065 mm. The extremity is 

 bluntly rounded and possesses a pair of very minute papillae. 

 In situ the tail end is sometimes found spirally rolled and 

 lying in a little gland-like mass of fatty and fibrous tissue, 

 but often occurs lying in line with the preceding part of the 

 body. 



The ridges in this species are irregularly wavy and 

 extremely low, their greatest height being under two micra 

 (fig. 27). In the mid-region of the worm they are fairly 

 regularly situated at '030 to '040 mm. apart. In the tail 

 region they are very low and close. At '6 mm. from its 

 tip they measured '015 to '017 mm. apart (body width 

 '16 mm.). Between two adjacent ridges there are two striae 

 and, sometimes, these latter are sufficiently pronounced to 

 make it difficult to distinguish them from the low ridges, 

 and then that portion of the worm S3ems to be minutely 

 corrugated. The ratio of the distance between adjacent 

 ridges • on the mid-body, to the mid-body diameter, is only 

 '2 as against '33 to '4 in the case of 0. gutturosa, and about 

 '08 to '10 in 0. gibsoni, where they are especially close. 



The oesophagus is '75 mm. long, its diameter increasing 

 from '015 to '02 mm. as it proceeds posteriorly. The vagina 

 lies at '48 mm. from the anterior extremity. 



Description of the Male. 



The male is a very delicate organism, apparently in- 

 habiting serous spaces in the connective tissues, not sur- 

 rounded by a tunnel — in this respect resembling the male of 

 0. gutturosa. The only specimen obtained — a broken one — 

 measures 23*8 mm. in length and possesses an even diameter 

 ('05 mm.) for nearly the whole of its length; narrowing 

 gradually to the spirally-wound tail, the width at the cloaca 

 being "03 mm. It is worthy of note that the head end has, 

 practically, the same dimension as that of the female. 



The head (figs. 6, 14) is rounded and bears at least two, 

 probably four, tiny papillae. Lips are not recognizable. 



