L.M.B.C. TURBELLARIA. 71 



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 

 Gorallina in tide-pools about Port Erin and on the 

 "Clets." It is recorded from Millport, Skye, St Andrews, 

 and Plymouth. 



24. Monotus fuscus, Oersted. (PI. 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 



