164 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
21. Cylindrostoma quadrioculatum, Leuck. (Pl. XIV. 
figs. 35 and 36.) 
Length 5—'75 mm. Body colourless, rounded in front, 
produced posteriorly into a long pointed “‘tail,” beset 
with adhesive papille. The pharnyx and its large cylin- 
drical sheath are long and muscular. The mouth is placed 
just in front of the brain, ‘The latter is quadrate, and 
bears two pairs of eyes: an anterior small pair, the lenses 
of which are directed backwards and outwards, and a 
larger posterior pair, whose lenses face forwards and out- 
wards. The sides of the body are occupied by a large gland, 
which produces food-yolk throughout its anterior portion, 
ova in the posterior. Hence it 1s called the germ-yolk- 
gland. The genital aperture is combined with the mouth, 
and through it the muscular penis containing both male 
secretions opens to the exterior. A large spermatheca les 
at the hinder end of the body. 
Cylindrostoma quadrioculatum occurs in tide-pools at 
the base of the littoral zone, near Port Erin. It is also 
recorded from Millport, Skye, and Plymouth. 
22. Cylindrostoma inerme, (Hallez.) 
This species resembles the former in many points, but 
is distinguishable from it by the following characters. The 
form of the body is stouter, the tail shorter. The bright 
yellow colour is due to small groups of pigment granules 
in the epidermis. The genital organs in general correspond 
closely to those of the foregoing species, but a spermatheca 
is absent. This form occurs among drift seaweed in Port 
Erin Bay and is also found at Plymouth. 
Family—Monotipaé. 
23. Monotus lineatus, O. F. Muller, (Pl. XIV. fig. 39.) 
Length 2—2°5 mm. Body elongated, flattened, tapering 
anteriorly, armed with strong adhesive-cells posteriorly. 
