BY T. HARVEY JOHNSTON. 69 



irregularly alternate near the anterior border of the seg- 

 ment ; genital canals passing between the longitudinal 

 excretory vessels, and dorsally to the nerve ; vas deferens 

 coiled, vesicula seminalis absent; "uterus persistent, sac-like 

 but may be subdivided into numerous, small communicating 

 chambers incompletely separated by partitions infolded from 

 the wall of the uterus, so that in some cases the eggs appear 

 almost as if isolated in the parenchyma." 



In Monopylidmm, there may be a single or a double crown 

 of hooks, the genital pores alternate irregularly, and the 

 ducts either pass* between the longitudinal vessels or 

 dorsally to them. The other features are the same as those 

 in Choanaf(i'iii<(, with the exception of the uterus, which .'s 

 here strongly branched, and finally breaks down into capsules 

 which usually contain one egg. 



We are now able to compare our parasite with these two 

 related genera. The scolex is unarmed in the species under 

 review, but is armed in the representatives of the two 

 genera. The male and female genitalia conform to the same 

 general plan in all three, and the genital pores are similarly 

 arranged. Besides this, the genital ducts pass dorsally to the 

 nerve and the ventral excretory vessel. In ChoanaUfma they 

 pass between the dorsal and ventral vessels; in MouojryJidium 

 they pass either between them or dorsally to both ; whilst in 

 our species there is only one vessel — the ventral — present, 

 and, as already mentioned, they pass dorsally to it. The 

 uterus in this cestode arises as a reticulum surrounding the 

 testes, very similar to that seen in Monopi/lidium passerimini 

 Fuhrm.f Ripe segments become filled with eggs, so that, at 

 first sight, one might be led to regard the uterus as being 

 sac-like ; but in section, it was seen to be made up of a large 

 number of chambers, which maintained their communication 



* Ransom, 1909, i.e., p. 76. 



t Fuhrniami, ()., Ceiitr. f. Bakt., Orig., 1, xlv., 1908, p.o28. Johnston, 

 T. H., Journ. Proc. Roy. Soc. N. S. Wales, xliii., 1909, p. 405. 



