8 W. BALDWIN SPENCER. 



into folds. Similar oues are noted by Stiles as present in P. 

 proboscideum; but as in the latter, so in P. teretius- 

 culum, they vary considerably, the examination of some 

 specimens leaving no doubt that true papillae are present, 

 whilst the examination of others will leave equally little doubt 

 that we are dealing simply with structures due to the wrinkling 

 of the cuticle and body-wall. After careful examination I 

 have been unable to detect their presence in sections. 



Reproductive Opening. — This serves at once to distin- 

 guish, apart from the size of the two, the male from the female 

 form. The opening of the vagina is placed on the mid-ventral 

 surface on the eighth annulus from the posterior end (fig. 1), 

 though the modified part around the opening may extend on 

 to the annuli next in front of and behind this one. The 

 opening itself is crescentic in shape, the hinder wall being 

 formed by the anterior part of a low, rounded, and swollen 

 cushion-like structure : the anterior wall is swollen and tumid. 

 The cuticle which lines the opening is thick and yellow 

 coloured. 



The anus lies at the very posterior end, between the two 

 lateral halves of the terminal annulus, the cuticle passing in 

 from the exterior. 



(ii) The Male (figs. 4 and 5). — In this the general form of 

 the body, the hooks, mouth, anus, &c., agree with the descrip- 

 tion given of the female ; the chief differences of importance 

 are (1) the size and (2) the position of the reproductive 

 opening. 



The length of a large-sized specimen is about 13 mm.; the 

 greatest width (which occurs just behind the head region) is 

 about 2 mm. Whilst the size of the male is so much less 

 than that of the female, the number of annuli is greater, the 

 average being about eighty-eight, the number varying within 

 one or two of this. 



Reproductive Opening. — The position of this at once 

 distinguishes the male. It has the form of an oval opening 

 with a raised tumid margin, the whole being placed on the 

 third and fourth annuli in the mid-ventral line, and with the 



