432 THOS. H. MONTGOMERY jrs, 
with parenchym (Par). But in the remaining trunk region, that is 
for the greater part of the length of the animal, four cavities may 
be distinguished: the lateral body cavities, the unpaired medio-dorsal 
cavity, and the unpaired medio-ventral cavity. 
The lateral body cavities are placed one on each side of 
the mid line throughout the greater region of the trunk, so that the 
median boundary of each is a dorso-ventral mesentery (L. Cav Fig. 63, 
Pl. 40). Laterally, dorsally and ventrally each of these cavities is 
bounded by the parenchymatous perienteric membrane (Per. M) of the 
corresponding side, before this membrane has become dislocated by 
oviposition. In the region of the most anterior ovaries (Fig. 61, 
Pl. 40) these cavities do not seem to be developed, since there each 
ovary is immediately enveloped by large-celled parenchym (L. Par). 
Each cavity is a long, unsegmented sack, semilunar on cross section, 
extending without interruption through the greater portion of the 
body though not quite as far forwards as the most anterior ovaries. 
These cavities are to be clearly determined in the adult stage only 
when the ova are being expelled from the ovaries (Fig. 63, Pl. 40). 
When the ovaries are filled with ova and before they have commenced 
to discharge them, the ovaries fill these cavities almost completely so 
as to practically hide them from view (Fig. 64, Pl. 40; Fig. 66, 
Pl. 41); but when the ovaries have emptied their contents into the uteri, 
‘the cavities are to be clearly seen with the ovaries projecting into 
them from their median walls (Fig. 63). The lateral body cavities are 
completely closed from the cavities of the ovaries and uteri. They 
extend posteriorly as far as do the ovaries. | 
The medio-dorsal cavity (M.D.Cav Figs. 63, 64, Pl. 40; 
Figs. 65, 66, 68, Pl. 41) is a smaller space and appears to be entirely 
closed off from the preceding cavities; it is bounded laterally and 
ventrally by that portion of the mesenteries (Mes) above the uteri (U?), 
and dorsally from the musculature (Muse) of the body wall by a 
deflected layer of the same mesenteries, though this layer is not every- 
where continuous. This cavity has on cross section generally the form 
of a triangle with the base directed dorsad. It does not extend for- 
ward as far as do the lateral cavities and the ventral cavity, but ends 
anteriorly about 4.33 mm behind the anterior end of the head. In 
the region of the posterior ovaries this cavity and the lateral cavities 
become confluent (Fig. 70, Pl. 41), and the common cavity thus formed 
is subdivided by bridges of large-celled parenchym. 
