AVIAN CESTODES. 863 
occupies the whole ventral surface of the proglottid. The ex- 
tension of the testes anteriorly in the segment seems to be 
prevented by the paruterine organ, which in those proglottids 
where the testes are fully ripe extends backwards for about half 
the length of the proglottid and takes up the greater part of the 
available space. It is important to insist upon the fact that 
the testes surround the female gonads, since this does not appear 
to be the case with other species of this genus Rhabdometra as 
figured by Ransom. The genus is, in fact, partly defined by the 
existence of the testes only behind and at the sides of the female 
organs. The testes are only two deep in a given segment. 
The cirrus-sac is long and slender, longer than that of the 
species figured by Ransom, but considerably shorter than the 
cirrus-sac of RA. nwmida of Fuhrmann, which reaches to the middle 
of the segment. In segments where the gonads are ripe but in 
which there is as yet no uterus, the cirrus-sac very nearly reaches 
the middle of the segment; but in older and wider segments it 
only just crosses the ventral water-vessel. Its course is obliquely 
forward from the point of opening on to the exterior, which is 
vather behind the middle line of the proglottid. There can 
hardly be said to be a genital cloaca : a funnel-shaped depression 
of the body, into the bottom of which the genital ducts open (the 
male duct anterior to the female), not showing the characters of 
a distinct chamber such as that of, for example, Hugonodeum. 
In horizontal sections the cirrus-sac often has a serpentiform out- 
line, being like an elongated S$. Occasionally it is slightly dilated 
at the internal end, but the cirrus-sac of this Rhabdometra never 
has the bottle-like form of that of many other tapeworms. In 
consequence of its length and slenderness the cirrus is not much 
coiled within it, lying mostly straight or rather in an undulating 
line. I could detect no spines upon the cirrus when protruded. 
I did not observe any autocopulation. The walls of the cirrus- 
sac are thick and very muscular. The internal coat is of cir- 
cularly running fibres, the outer layer fibres run longitudinally. 
From the internal end of the cirrus a retractor muscle runs for 
some way into the medullary tissue. This character is also found 
in other species of the genus Rhabdometra. The vas deferens 
forms a large coil which is situated posteriorly to the paruterine 
organ, and extends backward in the pvoglottid to as far as the 
receptaculum seminis. At about this point the efferent tubules 
from the testes meet it. There is no vesicula seminalis. 
The ovary lies at about the middle of the segment. It is in 
front of and larger than the vitelline gland: 
The vagina is long and thick-walled, and outside of the mus- 
cular walls is a layer of stalked glands which are deeply stained 
by hematoxylin. The course of the vagina is directed parallel to 
and slightly away from the cirrus-sac to begin with; it then 
curves more backwards to open into the receptaculum seminis. 
Its course is apt to be rather undulating. Ransom has figured a 
sudden change in the character of the vagina in the species 
