402 THOS. H. MONTGOMERY jr., 
The mouth opening is a small longitudinal split, placed at the 
anterior end of the head, in the male usually nearly terminal (Mo 
Figs. 1, 3, Pl. 37), in the female subterminal or more nearly ventral 
(Mo Fig. 2). The hypodermal cuticula is thickened at the mouth 
aperture, and there forms a rounded projection directed inwards 
(Fig. 1), its axis a hollow tube and not closed; this cuticular thickening 
seems to be more pronounced in the male. The anterior region of 
the intestine from the mouth opening to just behind the brain may 
be termed the oesophagus (Oes Figs. 2, 3); it is the narrowest portion 
of the intestine, lined by rather cubical cells (Oes Fig. 13, Pl. 37; 
Figs. 15—17, Pl. 58), and externally surrounded on all sides by the 
parenchym (Par) of the head region. Behind the brain there is a 
considerable dilatation of the intestine, which, since it stands in im- 
mediate connection with the radiating fibres of the muscular diaphragm 
(described with the musculature), may be regarded as a sucking or 
pumping stomach (Stom Fig. 14, Pl. 37). Through the greater region 
of the trunk is found what may be termed the middle intestine (Int 
Figs. 61, 63, 64, Pl. 40; Figs. 65, 66, 68, 70, Pl. 41), a ventral tube 
lying above the nerve cord in the medio-ventral body cavity, and ex- 
tending backwards nearly to the cloaca. This portion is composed of 
an irregularly folded, cubical epithelium, with large nuclei whose long 
axes are parallel to the long axis of the intestine; the cells appear 
for the most part highly degenerate (Int Fig. 21, Pl. 38). Bounding 
this epithelium is a layer of a denser and more homogeneous sub- 
stance (Int. S), without nuclei, with short radial projections; it cannot 
be determined from the adult condition whether this is a true basement 
membrane (a formation of the epithelial cells themselves), or e. g. a 
modified parenchym layer, but the absence of nuclei would speak for 
the former view. In this region of the body the intestine is ventrally 
attached to the parenchym lining of the nerve cord. At the posterior 
end of the female (Figs. 66, 68, Pl. 41), the receptaculum seminis 
(Rec) lies immediately above the nerve cord (N.C) and here forces 
the intestine (Int) out of its original position, so that the latter comes 
to lie variously either upon the side of or above the receptaculum. 
In the female, from this nearly axial position the intestine passes 
straight backwards to the dorsal side of the atrium (Air Fig. 74, 
Pl. 41), there becomes imbedded in the small-celled parenchym sheath 
(S. Par) of the atrium, and finally opens into the lumen of the posterior 
end of the atrium, or in other words, the anterior end of the cloaca. 
This most posterior region of the intestine (P. Int Fig. 74, Pl. 41) is 
