NEW AVIAN TAPEWORM. 213 



segments, as has been pointed out in considering the external 

 clin.ia.(tters of tliis worm, are enormously swollen so as to be 

 almost globular in form, except for the frill-like posterior end of 

 each proglottid, where it overlaps the one next in order behind it. 

 It would be easily supposed that this tension of the proglottids is 

 simply a matter of their being goi-ged with ripe eggs, such a 

 dilatation of proglottids seen in other tapeworms being due to 

 this cause. A microscopical examination, however, of such pro- 

 glottids shows that this conjecture is wi-ong. By far the greater 

 part of the interior of the proglottid contains no uterus or egg at 

 all. Fully three-quarters of the area of the proglottid is quite 

 empty of eggs, and the medullary substance only contains a few 

 fragmentary remains of other parts of the sexvial system — as I 

 suppose, for I have not identified the vestiges in question with any 

 certainty. Moreover, the dilatation is not due to the imbibition 

 of fluid during the processes of preservation. It was as obvious 

 in proglottids shed during the life of the bird as in those extracted 

 from the gut after death. 



I have examined such proglottids in both transverse and longi- 

 tudinal sections. Both sets of sections pi-ove that the ripe eggs 

 (or rather embryos) are only present posteriorly in the segment. 

 In one proglottid, which was completely cut into sections and 

 mounted upon ten slides, no less than seven of these slides 

 showed no end)iyos at all scattered through the parenchyma ; 

 in another proglottid, however, treated in the same way, embryos 

 were found to lie in the more anterioi- region, though here also 

 the most anterior pait of the proglottid was devoitl of eggs. 

 In both of these specimens, however, and in several others which 

 I have examined by means of sections, the ripe embryos or masses 

 of embryos by no means occupied the whole of the parenchyma. 

 There were large tracts of parenchyma quite uninvaded by the 

 uterus or its remains. 



The fact that the masses of eggs may in some cases lie rather 

 more anteriorly in the segment than they are apt to do in less 

 fully ripe proglottids is, as I think, in favour of Dr. Benham's 

 view that a scattering of eggs takes place owing to a i-upture of 

 the uterus when the pi'oglottids come apart *. The parenchyma 

 in these ripe proglottids must now be considered, as its condition 

 is doubtless related to the changes in the uterus that remain for 

 description. In younger proglottids, such as those represented in 

 text-figure 24, the parenchyma is firm in appearance, moderately 

 stained by carmine, and with abundant veiy well-stained nuclei ; 

 these nuclei seem to have a prevalently dorso-ventral arrangement 

 in lines. Calcareous corpuscles are abundant, especially towards 

 the posterior region of the segment, where the generative organs 

 are situated. In still older proglottids, which, however, are not 

 yet detachable from the strobila, such as those represented in 

 text-figure 29, the medullary parenchyma has taken on a 



* Quart. Joun). Micv. Sci. vol. xliii., 1900. 



