100 Transactions of the Royal Canadian Institute, [vol. x. 



account of the extremely small size of these fibres it was found impossible 

 to determine whether they are arranged in one or more layers. The 

 following are the averages of the measurements of four vesiculae semin- 

 ales : — 



Length. Width. Depth. 



0.140 mm. 0.092 mm. 0.090 mm. 



The vas-deferens narrows very abruptly again to a diameter of 15^ 

 as it enters the postero-dorsal portion of the cirrus-sac (Fig. 17) to 

 become the ductus ejaculatorius. This portion of the duct 

 takes three of four turns in the dorsal third of the cirrus-pouch and then 

 passes on as an enlargement, the second vesicula seminalis, 

 occupying approximately the middle third of the pouch (Fig. 38). 

 While the walls of the proximal portion of the ductus ejaculatorius quite 

 closely resemble in structure those of the vas deferens behind the larger 

 or posterior seminal vesicle, those of the distal vesicula seminalis are 

 very thin, showing few nuclei closely applied to the basement-membrane. 

 The diameter of the duct at this point is about 38/x. As the junction 

 between the ductus ejaculatorius and the inner vesicula seminalis is 

 approached the epithelium becomes broken up into numerous processes 

 which, however, did not appear to be true cilia. As a matter of fact 

 cilia do not seem to present in any part of the male reproductive ducts. 



The third division of the vas deferens within the cirrus-pouch, the 

 cirrus proper, usually commences at the posterior pole of the 

 latter, courses forward and then backward again to pierce the wall of the 

 pouch and open on the ventral surface of the proglottis at the point 

 shown in Fig. 17. The diameter of the cirrus at the bend in its course 

 (Fig. 38, c) is about 20/^; it enlarges gradually to 2>0fx before opening to 

 the outside. 



This region of the male duct can be evaginated, presumably, as in 

 most cestodes, to form a copulatory organ, yet in all the material at hand 

 not a single case of everted cirrus was observed. Consequently, nothing 

 can be offered, in regard to its function, apart from the suggestion that 

 from the frequent approximation of the male and female genital-openings, 

 noted above, self-fertilization may possibly occur in this species. The 

 structure of the cirrus would at least indicate that after eversion it might 

 become quite an efficient organ. Its wall (Fig. 24) is composed of an 

 inner lining of cuticle thrown into folds of varying heights, supported by 

 a basement membrane which can be distinguished as such only in young 

 stages. Outside of the latter appear two sets of circular muscles (Fig. 

 24, cm), separated by a comparatively clear protoplasmic area which is 

 traversed by the longitudinal and the retractor fibres (rmp) and numerous 



