106 MARINE FAUNA OF ST. ANDREWS. 



gliding over the surface of rock or glass like a living skin, 

 which requires a keen eye for detection. When much disturbed 

 they swim a short distance through the water, with a horizontal 

 stroke that has been compared by some to the motion of a 

 skate ; but the undulation in the former is much greater than 

 in the latter, which has a gliding or skimming character. 

 They also progress on the surface of the water. Even more 

 active and irritable than the Nemerteans, they move with ease 

 and swiftness — never avoiding any small obstacle, but spread- 

 ing their thin mobile bodies over it, and continuing their 

 course uninterruptedly. Occasionally when a projecting point 

 is attained, the anterior part of the body is elevated and waved 

 in and fro till a convenient branch of seaweed or zoophyte is 

 readied. Some are very prettily coloured; and though the 

 large and gaudily striped Eurylepta vittata, so characteristic 

 of our southern shores, is not found, yet the pink and yellow 

 hues of Planaria ellipsis are scarcely less attractive. The 

 little Planaria ulvce, which abounds in the brackish waters of 

 many of the creeks on the western coasts, is absent. The 

 common Leptoplana flexilis may be kept for months in con- 

 finement ; but it is perhaps less hardy in this respect than 

 tire Nemerteans. Even though it perishes, however, it fre- 

 quently deposits pale brownish masses of agglutinated ova on 

 the side of the vessel ; and the development of these can easily 

 be followed. 



Subclass TURBEhhAKlA. 

 a. APROCTA, Max Schultze. 



Order I. DENDEOCCELA. 



Fain. Leptoplanidae. 



Genus Lei'TOPLANA, Ehrenberg. 



Leptoplana subauriculata, Johnston, Catalogue of the Non- 

 parasitical Worms, Brit. Mus. p. 6. 



Common between tide-marks. 



