L.M.B.C. TURBELLARIA. 65 



occurs, produced at regular intervals into spinous pro- 

 cesses. The use of this organ has not been definitely 

 ascertained. It appears possible that it may have some 

 use as an offensive weapon. It this connection another 

 member of ihis family, Gyrator hermaphroditus, (found in 

 fresh-and sea-water in this country) is suggestive. The 

 so-called copulatory-organ is here converted into a stylet 

 enclosed in a sheath and provided with protractor and 

 retractor muscles. According to Hallez, it plays no part 

 in copulation but enables the animal to seize the Entom- 

 ostraca upon which it feeds. On approaching one of these, 

 Gyrator bends the hinder end of the body (containing the 

 stylet) downw^ards and forwards and stabs its prey re- 

 peatedly, which is then taken up by the pharynx. 



Pseudorhynchus hifidus occurred among drift-weed in 

 Port Erin Bay. It is also recorded from St. Andrews 

 where it was first discovered by Prof. M'Intosh ; and from 

 Millport. 



12. Acror]iync]iuscciledonicus,C\2^-^.i^\.XlTl,^g?>.l^,20.) 



Length 1 mm. Body elongate, cylindrical, slightly 

 tapering anteriorly. Colour white w4th grey blotches, the 

 pharynx pure white. The dermal musculature, as in 

 most representatives of this family, is very strong, and 

 enables the animal to bear compression under a cover-slip 

 without rupture. A mature animal treated in this way 

 displays the complicated reproductive organs with almost 

 diagrammatic clearness. The granule-and sperm- vesicles 

 are bound together in a common penial muscular sheath 

 which leads into a copulatory organ armed with small 

 knobbed chitinous spines. 



This form is frequently obtained among sea- weeds 

 between tide-marks at Port Erin, and also occurs at Skye, 

 Millport, and Plymouth. 



