(t. H. F. Nuttall 
807 
(F. pen.f.) which appear at times very confusing in sections; the teeth 
are mostly directed toward the genital orifice. When the vesica is 
extruded it is seen to gUde outward upon the basal plate (PL III, fig. 2) 
and the teeth alter their direction as illustrated in the figure. The penis 
is seen lying within the invaginated vesica, its distal extremity pointing 
into the cleft in the dilator (PI. Ill, fig. 1, DU. cl.), through which it is 
propelled. The base of the penis is continuous with the statumen penis. 
The latter may be regarded as merely a rod-like thickening of the vesica 
wall, it shows some variation in appearance and size in different in¬ 
dividuals, it measures 0-45-0-70 mm. in length but is difficult to measure 
because of its curvature. Basally, the statumen protrudes more or 
less from the inverted vesica, at this point it is broad and twisted and 
shows faintly visible chitinous strands which indicate where muscle 
fibres are inserted; its shaft is slender and bandlike, about midway it 
sends off a retrograde flattened branch which curves about it, and 
distally, near the base of the penis, it shows a large asymmetrical pro¬ 
trusion which is best seen when the parts are isolated (PI. Ill, fig. 3). 
The appearance of the vesica when extruded has already been described. 
(4) The penis is a tubular structure, darkly chitinized, and tapering 
to a point, somewhat like that of a quill pen. Its length varies, measuring 
from 0-24 to 0-32 mm. in the specimens examined. It is broadest 
basally, where upon its internal surface there are fine granulations and 
striations where muscles are inserted. Its shaft tapers to about a 
width of 20p,, and distally it ends in a fine point or points of very thin 
colourless chitin. Running through the lumen of the penis and clearly 
discernible is the ductus ejaculatorius. The penis protrudes from the 
left side of the evaginated vesica; its chitin is continuous with that of 
the vesica and statumen. 
(5) The ductus ejaculatorius is a very thin-walled, colourless and 
structureless tube of remarkably uniform width from near the tip of 
the penis to where it suddenly becomes muscular near the proximal 
end of the basal plate. Within the tube of the penis it measures 5-6 fi, 
posterior to this it may measure 7 /x, but possibly this slightly increased 
width may be due to flattening. In dissections of the inverted vesica, 
the duct can be distinctly traced from the base of the penis directly 
through the wall of the vesica, along whose dorsal surface it afterwards 
runs backward to the accessory glands. Basally, its muscular investiture 
sets in abruptly and rapidly grows in volume, the strong musculature 
doubtless being essential to force out the spermatic fluid through the 
long and minute duct. In one specimen the duct measured 1-1 mm. in 
