L.M.B.C. TURBELLARIA. 165 
The colour is white, frequently marked with brown pig- 
ment. The epidermis contains numerous flagella. The 
anterior end is used in an extremely sensitive way. 
Immediately upon encountering any obstacle it is sharply 
retracted, and the hinder extremity at the same moment 
grasps the substratum by its shield-shaped adhesive sur- 
face. This is done so rapidly that it becomes difficult to 
surprise the animal and capture it by means of a pipette. 
A short distance from the anterior end an otolith is 
constantly present in members of this family, and in front 
of it is a median transverse band of pigment usually 
spoken of as the ‘“‘eye.”” The pharynx is inserted near 
the centre of the body, and is extremely contractile. The 
germaria, two in number, are placed at the sides of the 
base of the pharynx. The penis is characteristic of the 
species. It is merely a soft papilla receiving the contents 
of the muscular vesicula seminalis, and transmitting them 
to the exterior through the male pore, which is placed 
behind the female pore, a short distance from the posterior 
end. Monotus lineatus occurs not uncommonly among 
Corallina in tide-pools about Port Erin and on the 
“‘Clets.” It is recorded from Millport, Skye, St Andrews, 
and Plymouth. 
24. Monotus fuscus, Oersted. (Pl. XIV, figs. 37 and 38.) 
This species resembles the former in many external and 
internal anatomical features. The colour however is rather 
different. The anterior end is whitish, the rest of the 
body brown. Von Graff and Jensen record individuals 
with purple pigment. 
The changes of colour undergone by young Monotus 
in reaching the adult condition are the following, as v. 
Graff has already noticed. Very young specimens (1 mm. 
or so,) are white, with a few carmine granules. Next, 
these granules increase in number, giving a reddish tint 
