552 DR. F. E. BEDDARD ON 



a layer two or three cells deep, of which the outer ones are close 

 to the cuticle. On tire other hand, in Ptychohothrium belones the 

 moi-e scanty subcuticula lies in the parenchyma some way below 

 the cuticle. I find on a re-examination of sections of Hyracotcunia 

 hyracis * that the subcuticula occurs in patches on the mature 

 segments, and seems, therefore, to be in course of disappearance. 

 It is, moreover, mentioned by Gough t that in Stilesia the sub- 

 cuticular layer is not to be foimd in "^ older portions of the strobila. 

 in segments where the paruterine oi'gan is fully developed." 

 Gough holds that this absence of the subcuticula in mature 

 segments is a secondary character. The state of aflairs seems to- 

 bear out the suggestion that in my Dipyliditmi the subcuticula 

 has actually disappeared in the mature segments. 



The testes occupy all the available space in the proglottids, and 

 are thus mainly between and posterior to the ovaries. In the 

 more elongated and riper proglottids the testes are only one row 

 deep and not more than 6-9 (according to the length of the 

 segment) in a single row; they are thus evidently not so 

 numerous as in some species. 



The two generative orifices lie one on each side of the body not 

 far from the anterior boundary of the proglottids. The cirrus-sac 

 is in front of the vagina, and, as is shown in sagittal sections, in 

 the same straight line with it, being neither dorsal nor ventraL 

 The cirrus-sac has very definite, rather thick muscular walls,, 

 which are even quite obvious when the sac is dilated in mature 

 segments, though not so thick in appearance. The cirrus is long 

 and mucli coiled within the cirrus-sac. The sperm-duct is also 

 much coiled, and the two sperm-duct coils very nearly come into- 

 contact in the middle of the segment. 



The ovaries of this Dipyliclium are, as a rule, clearly two in each 

 proglottid lying rather laterally and anteriorly. They are, in fact,, 

 like those of other species, such as D. zscTioTikei of Hungerbiihler,, 

 as to their position in the proglottid. But I do not find in cases- 

 which I have particularly examined that there is an absolutely 

 complete separation between the two ovaries of a given proglottid. 

 In this matter I refer to rather anterior proglottids which are 

 not elongated and stufied with ripe eggs containing embryos. 

 However, in other proglottids I found a distinct separation between 

 the two ovaries, the fact being that they approach very near to- 

 each other in the middle line of the segment. There is, however,, 

 no doubt about the entire separation of the vitelline glands, each 

 of which lies behind the ovary of which it is an adjunct. The 

 ovaries occupy a good deal of the space in the short jDroglottids. 

 where they occur when full sized. They are posterior to the coils 

 of the vas deferens, but reach very nearly to the posterior end,, 

 where the testes occur ; the testes also occupy the available space 

 between them. 



The receptaculum seminis penetrates the middle of the ovary 



* For species, see P. Z.S. 1912, p. 593. 



t " A Monograph of the .... Avitellina?," Q. J. M. S. Ivi. 1911, p. 345. 



