AVIAN CESTODES. 877 
facts which I have described above in connection with the 
formation of the uterus in Lhabdometra cylindrica. I have 
mentioned that the uterus soon after its formation is distinctly 
retiform, the network being irregular but very plainly to be seen 
in horizontal sections. In transverse sections, the uterus is 
seen to lie ventrally and to consist of variously sized cavities 
detached from each other, which is, of course, the expression of 
the horizontal network when seen in that aspect. In more 
mature proglottids the retiform condition is not so clear and the 
uterus occupies much more of the proglottid. The arms of the 
network seem to have coalesced, forming an irregularly shaped 
body with partial septa dividing its interior into partly detached 
cavities, and with outgrowths producing a general irregularity of 
surface. In the completely mature proglottids the appearance 
of the uterus has again changed owing to further development. 
Text-fig. 10 shows a transverse section of such a proglottid, and 
the contained uterus is seen to be circular in section and thus to be 
rod-like in form. Posteriorly the uterus is divided by a median 
septum into two equisized halves, but further forward the uterus 
is obviously single, but the interior is divided by many ingrowing 
strands of the medullary tissue into a series of chambers each of 
which is seen to lodge butasingle embryo. The posterior division 
of the uterus into two reminds us of the uterus of Rhabdometra 
mgropunctata as figured by Crety* ; it is possible, however, that the 
latter form is rather to be referred to the genus Metroliasthes, in 
which the uterus is an entirely double structure. The series of 
changes in the appearance of the uterus in this species of 
Rhabdometra is very remarkable, and seems to contrast with what 
has been observed in the other species of the genus. It is 
further to be noted that we have here, as a temporary phase, a 
form of uterus which is now characteristic of one genus of 
Tapeworms and now of another. 
From the above account we can abstract the following de- 
seription of the species :— 
Rhabdometra cylindrica, sp. n. 
Length 150 mm.; greatest diameter 1:2 mm. Scolew of less 
diameter than strobila following, suckers proportionately very large ; 
rostellum and hooks absent. Neck absent; posterior segments 
elongated, five times their diameter, cylindrical in form. Genital 
apertures alternate regularly, behind middle of proglottid. Genital 
ducts pass between water-vessels and ventral of nerve-cord. Cortical 
layer thick ; longitudinal muscles not in strong bundles ; mostly 
implanted singly, but a row neat to transverse layer of widely 
spaced bundles with from two to five or six fibres. Circular layer 
* Boll. Mus. Torino, 1890. In Crety’s figure the two posterior and globular 
diverticula of an anterior curved portion are alone represented as containing eggs: 
I assume, therefore, that the anterior part is all of it to be regarded as a paruterine 
organ, 
59* 
