TWO NEW TAPEWORMS. 697 



Cestodes, and occurs for instance, in the present genus, in 

 Linstowia ameivce. The cirrus-sac itself is oval in longitudinal 

 section, and at times almost circular. It has a thickish external 

 muscular layer, and is not differentiated into regions as is 

 sometimes the case with the cirrus-sac, where the internal region 

 is thinner- walled and occasionally swollen. Owing to the small 

 size of the cirrus-sac, the contained cirrus and vas deferens are 

 not much coiled, and the lack of room has brought about quite a 

 short cirrus, which is of about the same length as the section of 

 the vas deferens wdiich lies within the ciiTus-sac. As in other 

 Cestodes, the contents of the cirrus-sac (which together with 

 the external muscular layer forms the wall of the cirrus) and a 

 section of the vas deferens can be extruded with the cirrus. 

 To this complex it is perhaps convenient to give the name of 

 penis, as 1 have elsewhere suggested. 



The vas deferens on emerging from the cirrus-sac forms a 

 loosely arranged coil which lies to the ventral side of the cirrus- 

 sac, the interstices between the coils being filled with glassy 

 cells — the so-called prostate. Upon this ensues a straight 

 course of vas deferens, which lies upon the dorsal side of the 

 cirrus-sac in relation to the dorsal position of the testes. 



The ovary is seen in ti'ansverse sections to lie dorsally of the 

 vitelline gland. It has a structure common in Cestodes, ending 

 laterally in numerous drawn-out processes which are often club- 

 shaped at the free extremities. The ovary extends further 

 laterally than the vitelline gland, which it thus completely over- 

 laps. It is, of course, also anterior in position. 



The vagina of this Cestode shows the same subdivisions in its 

 course that are shown in other Cestode woims, though the 

 relative development of the different sections differs in various 

 genera and species. In the present species the general course of 

 the tube is fairly straight until it divides into the oviduct 

 and the second branch. In mature segments, in which the 

 utervis is still present, though many eggs are scattered through 

 the parenchyma, it can be seen that the vagina consists of four 

 separable regions. The proximal section, opening into the 

 common genital duct befoi-e the latter debouches into the cloaca 

 genitalis, is very short, with thick walls and a narrow lumen. 

 The next section occupies the greater part of the vagina, and 

 consists of a tube which gradually widens and ends in the 

 neighbourhood of the ovary in a dilated extremity. This section 

 is covered externally with a layer of deep-staining glandular 

 cells which mark it out from the preceding section. This part 

 of the vaginal tube is specially developed in the present Cestode, 

 and in fully mature proglottids, where the parenchyma is entirely 

 occupied by the scattered embryos encircled with their mem- 

 branes, is the most conspicuous region of the vagina ; it presents 

 here the appearance of a large sac. It is, in fact, here almost 

 divisible into two regions : a narrower part which is proximal, 

 and which — wide itself — dilates suddenly into a large oval sac 



Proc. Zool. Soc— 1916, Ko. XLVDI. 48 



