72 TEANSACTIONS 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. 



Moiiotus 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 pro- 

 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 scraping Balani 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 halani. 

 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 halanoides 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 

 Erin, Millport, and Plymouth. 



III. POLYCLADIDA. 



A. AcoTYLEA : Family — Leptoplanid^. 



24. Leptoplana tremellaris, 0. F. Mull. (PI. XIV, fig. 40.) 



Length 20 — 25 mm. Body deHcate, slightly 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, 



