312 
StHfUes on Pediculus 
base to their insertions were put upon the stretch between two fine 
needles, and, whilst stretched upon the slide, the preparation was fixed 
by dropping Carnoy’s solution upon it; the specimen was afterwards 
stained and mounted in balsam. 
The retractor muscles of the basal plate (Text-figs. 2, 3, M. retr. pi.) are 
relatively few. They arise from the ventral intersegmental fold bounding 
the seventh abdominal segment anteriorly and pass backward to their 
insertions laterally near the anterior end of the basal plate; these 
muscles mil serve to retract the plate gently into the body. 
The return of the dilator to its resting position is due to the relaxation 
of its flexor muscles and its elastic rebound upon its basal articulation; 
similarly, as the pressure of the vesica within the cleft lessens, the 
rebound of the chitin surrounding the cleft causes the lumen of the 
latter to narrow. When at rest, the axes of the dilator and basal plate 
fall into fine. 
The ductus ejaculatorms (Text-fig. 4, D. ej.) runs between the retractor 
muscles of the vesica and enters the latter at the base of the penis. 
The duct is therefore propelled passively with the sack when the latter 
is extruded, and it is also retracted passively. 
Judging from the presence of a few muscle fibres attached to the 
posterior thickened wall of the pregenital fold (Text-fig. 3, p. pi.), these 
muscles may serve to occlude the lumen of the genital aperture and 
perhaps aid in the act of defaecation by raising and pushing forward 
the anal papilla. 
The Female Apparatus. 
The structure of the female copulatory apparatus is very much 
simpler than that of the male. Its position is shown in Text-figs. 6, 7 
and 9. It is situated ventrally in the last three segments of the body. 
The vaginal orifice (Text-figs. 6 and 9, vag.) appears as a transverse slit 
occupying the greater portion of the width of the last segment, and 
immediately dorsal to it lies the anal orifice {An.) between the two 
terminal lobes of the body. In darkly pigmented specimens, a sharply 
defined, darkened area of thickened chitin of characteristic form, covers 
a part of this region ventrally (Text-fig. 6, v. pi.), and posterior thereto 
occur the paired, so-called gonopods which are usually pigmented (Text- 
figs. 7, 9, Gon.). The gonopods are in the form of flat incurved hooks 
which overlap sUghtly behind and whose inner concave margins are in 
continuity anteriorly through a concave fold of the integument; this 
fold and the inner margins of the hooks, bound a subcircular space 
