166 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
to the individual. Lastly, the red colour of the granule 
gives way to brown which appears when the specimens 
reach 1°75—2 mm. in length. 
Monotus fuscus ranges through the littoral zone to its 
higher portions where the rocks and weeds are exposed to 
the drying effects of the atmosphere. Turbellaria are 
however so constituted (being without any outer pyro- 
tective membrane) that dryness means death to them. 
It is interesting therefore to find M. fuscus adopting a 
singular device in order to gain a moist environment 
during the ebb-tide. Prof. Hallez, of Lille, in 1879, 
recorded that after scrapmg Balaww off the rocks at 
Wimereux, and placing them in a basin of sea-water, 
this form presently emerged. They had concealed 
themselves among the thoracic appendages of the Balani, 
and thus continued to keep their surface in contact with 
a moist medium. Hallez hence called it Monocelis balam. 
Prof. v. Graff has found that at low water M. fuscus 
occurs between the gills of Chiton and Patella, and he 
supposes that it leaves this situation when the tide returns. 
Balanus balanoides at Port Erin yielded several specimens. 
The copulatory organ has the form of a tubular chitinous 
duct, attached by muscles to the mouth of the vesicula 
seminalis. 
Monotus fuscus occurs between tide-marks at Port 
Hrin, Millport, and Plymouth. 
ii; POLYCLADEDA 
A. AcoTYLEA: Family—LEPTOPLANIDA. 
24. Leptoplana tremellaris, O. F. Mull. (P1. XIV, fig. 40.) 
Length 20—25 mm. Body delicate, shehtly expanded 
in front, the anterior margin being almost semi-circular. 
Swimming is effected by repeated violent vertical strokes 
of the expanded margins. The colour is variable. White, 
