L.M.B.C. TURBELLARIA. 67 



the sub-family Hyporhynchinae) opens on the ventral sur- 

 face, behind the anterior extremity, and is much reduced in 

 size as compared with that of the Acrorhynchina). The 

 copulatory-organ consists of two spirally-coiled chitinous 

 tubes fused throughout the greater portion of their lengths. 

 Of these the finer duct transmits the granule-secretion, 

 the wider one enables the spermatozoa to reach the 

 exterior. The spiral takes two complete turns and ends 

 in a terminal straight portion where the two ducts sep- 

 arate from one another. 



This species was dredged in 15 fms. just outside Port 

 Erin Breakwater. It has also occurred at Plymouth. 



Family — Vorticid/E . 



16. Provortex halticus, Schultze (PI. XIII, figs. 27, 28.) 



Length '5 — "75 mm. Body cylindrical, truncated, in 

 the angles produced into blunt processes. The posterior 

 extremity forms a long, finely-pointed '' tail." The colour 

 is due to irregular brown pigment which appears to be 

 deposited as fine vacuoles in the cells of the parenchyma. 

 The pharynx which opens through the mouth just below 

 the anterior end, is provided with a distinct " seam" to 

 to the margin, furnishing a surface of inseition for the 

 strong pharyngeal retractor muscles. 



The copulatory organ is cylindrical. Its aperture con- 

 stitutes a slit, one margin of which is bent upon the 

 main-duct and ends in a free process of variable shape. 

 The uterus discovered by von Graff, lies in front of 

 the penis and contains a single yellow cocoon at a time. 

 A long fine duct leads to the genital aperture. 



This extremely active, tiny animal occurs plentifully in 

 tide-pools near the Port Erin Station. It is also recorded 

 from Millport and Plymouth. 



