HISTOLOGY OF THE LAND-PLANARIANS OF CEYLON. 
141 
The vagina is lined with a densely ciliated epithelium, which rests on a stroma of con- 
nective tissue ; the lumen of the tube in transverse section is, when the lining of the 
tube is in a contracted condition as here depicted, cruciform. A quantity of glandular 
matter of a branched thread-like form passes to the muscular mass containing the vagina 
from all sides. The irregular threads composing the gland break up into finer branches, 
which appear to become lost between the longitudinal muscular fibres of the vagina. I 
at first took these thread-like masses for nerves, but they are evidently homologous with 
the shell-making glands described by Keferstein (loc. cit. p. 28) in Lejptoplana tremel- 
laris , and figured originally in the same species by Mertens. The threads of the gland 
appeared to become continuous in places with the general glandular matter of the body, 
which is especially abundantly present in the neighbourhood of the generative organs. 
It may be that this shell-gland, so highly developed in Leptojplana, is here rudimentary 
and nearly functionless, or possibly it may be in a more active condition at a different 
period of the year from that at which I gathered my specimens of Bipalium. The 
uterus is provided, like the vagina, with strong circular longitudinal and radiating fibres ; 
it terminates (Plate XII. fig. 4) in a heart-shaped cavity, clothed with a very thick 
epithelial layer and densely ciliated. At the apex of the heart, i. e. inferiorly, there is a 
papilla, on each side of which opens one of the oviducts, which may be seen in the figure 
curving inwards to meet at that point, but remaining distinct from one another to the 
very last. It is probable that the aspect of both vagina and uterus becomes much 
altered when the egg-capsule is formed, if such be formed. The cavity is probably 
greatly enlarged, its muscular walls proportionally thinned, and very probably the 
uterine and vaginal tubes are run into one. 
The penis in Bipalium is more or less conical in shape. In the base of the cone is a 
large glandular cavity with a muscular wall, the prostate, into the anterior extremity 
of which open the vasa deferentia, and from which a tube is continued down the centre 
of the penis to its tip. The penis has an elaborate muscular structure, for which refer- 
ence should be made to Plate XII. fig. 5 & Plate XIII. fig. 3. The cavity of its central 
tube is lined with a glandular epithelium, which rests on spongy tissue : this is succeeded 
outwards by a dense circular muscular layer ; then follows a space occupied by radiating 
fibres, more or less intertwined, and having canal-like spaces in their interstices and also 
bundles of strong longitudinal fibres. Externally is a row of delicate longitudinal fibres 
and a thin layer of circular ones. Finally, the penis is covered with an epithelium, 
consisting of rounded vesicular elements. The cavity containing the penis is lined with 
a simple even layer of epithelium, divided by vertical lines into irregular elements, which 
are apparently without nuclei. The penis is attached to its sheath by means of its 
radiating and longitudinal fibres, which spread out and invest the large glandular cavity 
at its base or prostate, and thus form an ovoid muscular bulb. The cavity in this bulb 
or prostate is lined with a glandular epithelium disposed in a series of follicles 
(Plate XIII. fig. 2). The epithelium is of the same nature as that found lower down 
in the central tube of the penis, but is here especially developed : it is very conspicuous 
