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 
to and fro till a convenient branch of seaweed or zoophyte is 
reached. 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 
the 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 TURBELLARIA. 
A. APROCTA, Max Schultze. 
Order I. Dendroccela. 
Fam. Leptoplanidae. 
Genus Leptoplana, Ehrenberg. 
Leptoplana subauriculata, Johnston, Catalogue of the Non- 
parasitical Worms, Brit. Mus. p. 6. 
Common between tide-marks. 
