328 PROCEEDINGS OF SECTION D. 



as three tiny papillae on the outer side of the head, one corresponding 

 to the centre of each lip [compare figs. 6 and 7a). 



Cervical PapillcB. — These have not been observed in either 

 male or female. 



Excretory Pore. — As a rule no excretory ring and pore has been 

 observable externally, but in two females at 0.358 and 0.379 mm., 

 respectively, from the anterior end is a special development of 

 tissue carrying excretory vessels to the mid-ventral line, though the 

 excretory pore could only doubtfully be detected [see figs. 6 and 7). 

 In the male the excretory pore was only doubtfully distinguishable 

 in one case at 0.251 mm. from the anterior end. 



Vulva. — This, which often appears as a tri-radiate slit or a 

 circular opening on the mid-ventral surface, varies greatly in 

 position compared with the position of 0.8 mm. from the anterior 

 end given by Cleland and Johnston, namely, from 0.46 mm. in an 

 uncontracted specimen to 1.138 mm. in a specimen probably some- 

 what contracted, the most frequent position being at 0.57 to 0.69 

 mm. {compare figs. 5, 6, and 7). 



Tail. — In the male [compare fig. 9) this is very fine, gradually 

 tapering, somewhat bluntly pointed. The last part of the body is 

 coiled spirally once or twice ; the cloacal opening is (figs. 10 and 11) 

 a transverse slit which lies at 0.048 to 0.062 mm. from the tip of the 

 tail, the diameter of the body at this level being 0.042 to 0.051 mm. 

 We do not understand the figures given by the authors of the 

 species in reference to the position of the cloacal opening, namely, 

 " the anus in the male is situated at 0.072 mm. from the posterior 

 extremity," and then later on, " the cloacal opening is situated on 

 a median prominence about 0.65 mm. from the end of the parasite." 

 The latter figure should presumably read 0.065 mm., and is even 

 then slightly in excess of what our specimens show. 



The anal papilla are given by Cleland and Johnston in their 

 second account of the parasite as six pairs, with perhaps the repre- 

 sentative of another pair of papillae. Our specimens show very 

 clearly seven pairs (figs. 10-12b), not, however, always bilaterally 

 symmetrical or exactly comparable in different specimens. The 

 figure represents what appears to be the normal arrangement of 

 these structures, that is to say, there are three pairs ad-anal, one 

 pair pre-anal, and three pairs post-anal papilla. Of these the 

 pre-anal are usually somewhat large, well separated, and readily 

 seen (figs. 10 and 12a). Sometimes they are so far back as to be more 

 correctly described as an additional ad-anal pair (figs. 11 and 12b,, 

 and cf. Cleland and Johnston, loc. cit., Fig. 3), at other times these 

 two pre-anal papillae are very much closer to the median ventral 

 line. On one occasion there was one very clearly marked additional 

 papilla on the left side, some distance in front of the normal pre-anal 

 pair, but none could be detected on the right side (fig. 12b). The 

 three smaller ad-anal papillae on either side are, rarely, so closely 

 arranged as to appear almost continuous with one another at their 

 bases (fig. 11). The most anterior pair of post-anal papillae are 



