The adult organisation of Paragordius varius. 435 
becomes less in amount, and from the plane of the last pair of ovaries 
is continued forward as the perienteric membrane (Per. M). 
The perienteric membranes, the single representatives of the 
large-celled parenchym through the greater length of the trunk (Per. M 
Figs. 63, 64, PI. 40; Figs. 65, 66, PI. 41), are found on the sides of the lateral 
body cavities. They are separate from each other. Each bounds the la- 
teral, dorsal and ventral aspects of the body cavity of its side of the trunk, 
but not the median surface. Throughout the greater region of the 
trunk this is an epithelial layer of one cell thickness (Per. M Fig. 37, 
Pl. 39); but at its anterior and posterior ends this membrane becomes 
thicker, passing over gradually at these points into the thickened 
parenchym masses of these regions, as has been described above. The 
perienteric membranes are not firmly attached to either the muscu- 
lature externally nor to the walls of the ovaries internally, for when 
the ovaries are empty it is generally found disassociated from both 
these surfaces (Fig. 63, Pl. 40). Each membrane is deflected at its 
dorsal and ventral angles, and these deflected portions are apposed to 
the walls of the mesenteries but do not form an integral part of the 
latter. Each membrane appears to be a continuous sheet of tissue 
from before backwards, that is, is not segmented, and is composed of 
large parenchym cells. 
2) The small-celled parenchym. In the greater region of 
the trunk this is represented by the tissue of the mesenteries (Mes 
Figs. 63, 64, Pl. 40; Figs. 65, 66, Pl. 41), and by the deflected 
portions of these which line the medio-dorsal body cavity dorsally 
and the medio-ventral ventrally (here forming the envelope of the 
nerve cord). It is generally characterized by a relatively larger 
amount of intercellular substance, smaller cellular cavities, and nuclei 
rather more rich in chromatin. 
3) The fibrous parenchym is apparently a modification of the 
preceding, with still smaller cellular elements of elongate form, so that 
the tissue seems to be composed of concentrically placed spindle-shaped 
cells (S. Par Figs. 48, 49, 51, Pl. 40). This tissue starts posteriorly 
at the junction of the cuticular and glandular portions of the cloaca, 
forms a sheath next to the cloaca and further forward becomes thicker 
around the atrium (there also enclosing the most posterior part of 
the intestine, S. Par Fig. 74, Pl. 41), around the neck of the recepta- 
culum seminis (Rec.N Fig. 70, Pl. 41) and around the descending 
portions of the oviducts (Fig. 75); in the latter plane a modification 
