NEW AVIAN TAPEWORM. 207 



the length of the cirrus sac. When the entire system of genital 

 flucts is seen in longitudinal section, i. e. in transverse sections of 

 the proglottid, it will be obsei-ved that the cirrus sac projects into 

 the cloaca genitalis, and that the latter is therefore prolonged 

 backwards as a kind of collar surrounding the protrusible part of 

 the cirrus sac. Dr. Gough has figured in Stilesia hepatica* a 

 similar backward growth of the cavity of the cloaca genitalis. In 

 such longitudinal sections of the cloaca genitalis of Otiditcenia it 

 will be observed that the cavity is not so regular as I have seen 

 it in transverse sections ; there are lateral foldings of the lumen 

 which are probably paired and thus produce no appearance of 

 crumpling when the organ is viewed in transverse sections. 



The vagina and cirrus sac, of course, open into this cloaca, the 

 vagina nearer to the external orifice of the cloaca genitalis. 



In following out a series of sagittal sections of the proglottids, 

 which ai-e, of course, transverse to the direction of the cloaca 

 genitalis, it will be seen that, as a, rule, the cirrus sac becomes 

 separate from the vagina in a position which is at first obliquely 

 anterior to the vagina. This is the same on both sides of the body ; 

 but it is not invariably that the cirrus sac thus opens into the 

 genital cloaca anteriorly of the vagina. I have seen one case (text- 

 fig. 28, p. 208) in which the vagina lay anteriorly to the cirrus sac, 

 and in this case air obliquity occurred in the relative positions of 

 the two tubes, but the obliquity was in the reverse direction to that 

 shown in the normal arrangement. The obliquity, that is the 

 more dorsal or ventral inclination of the cirrus sac to the vagina, is 

 already known to vary; thus, in Monieza the position in i-elation 

 to each other of the two tubes varies according as to whether they 

 belong to the right or left side of the body, while in AviteUina 

 centripunctata Dr. Gough has figured, in his paper already referred 

 tot, an alternation of this kind in successive segments and on the 

 same side of the body. There is, however, here no question of a 

 reversal of an anterior to a posterior position such as I have found 

 in Otiditcenia eupodotidis. 



In one case I found another remarkable variation. This was 

 the complete absence of the proximal part of the vagina ; into the 

 cloaca genitalis opened only a cirrus sac. However, as the series 

 of sections in which I observed this variation was traced further 

 towards the middle line of the body, the median region of the 

 vagina, which is of small calibre, came into view. In any case, 

 the wide region of that tube which, in normal cases, opens into 

 the cloaca genitalis was completely absent, save, indeed, for a few 

 traces of its muscular longitudinal sheath. 



The vagina issues from the cloaca genitalis in an oblique 

 position, as seen when the worm is studied in a series of sagittal 

 sections, save, of course, for the exceptions mentioned above. It 

 runs parallel with and later in close contact with the dense coil of 



* "A Moiiot?raph of the Tapeworms of the Subfamily Avitelliniiia»," Quart. Journ. 

 Micr. Sci. vol. Ivi. 1911, pi. xii. fig. 16, at. 

 f Loc. cit. pi. xiv. fig. 43. 



