458 W. A. HASWELL. 
From this the median ejaculatory duct runs backwards to 
the penial opening. Laterally a pair of strands of granule 
(prostate) ducts pass within the penis sheath, and strings of 
granules accumulate on either side of the ejaculatory duct to 
form a granule reservoir. The unicellular granule or prostate 
glands are scattered through the surrounding region, extend- 
ing outwards nearly as far as the lateral border, and nearly 
to the posterior end. 
The muscular penis sheath encloses the vesicula seminalis, 
the ejaculatory duct, the granule reservoir, and the penis. 
Posteriorly it divides into two layers, one becoming continuous 
with the wall of the penis, the other with that of the genital 
atrium. 
The penis is a wide tube with thin and flexible walls, armed 
with chitinous teeth. The entire inner surface is beset with 
these teeth, which, extremely minute in front, become of 
relatively large size towards the opening of the penis into 
the atrium. The largest teeth, -08 mm. in length, vary in 
number in different individuals from three or four to twelve 
or more. The teeth are situated on the inner surface of the 
eversible penis when at rest, with their apices directed 
inwards, and must bristle outwards when protrusion takes 
place. Between the penis sac and the enclosed structures is 
a space filled with some uncolourable substance, through 
which extends in sections an irregular felt-work of fine 
filaments. This becomes closer towards the line along which 
penis sheath passes into penis, and, notwithstanding their 
extreme fineness, these fibres are doubtless muscular. It is 
the contraction of the muscular sheath that, acting through 
the contained fluid, must be the means of causing the eversion 
of the penis. Annular fibres constitute a sphincter of the 
sheath. The ejaculatory duct, traversing the penis, opens 
into a cavity of small size with muscular walls, into which 
the oviduct and bursa copulatrix open; this is the genital 
atrium. 
The single ovary lies close to the penis sheath, on its right 
side anteriorly. It is of compact elliptical form, with its long 
