480 Transactions of the Society. 



border revolute ; ciliary disc somewhat oblique, not elevated ; posterior 

 extremity attached to the pedicle through the intermedium of a small 

 button-like projection ; pedicle filiform, from seven to eight times as 

 long as the body, only the anterior portion contracting when the foot- 

 stalk is thrown into its small, irregular undulations rather than spiral 

 folds ; contracted body obovate, the button-like extremity invaginate 

 within the body ; endoplasm colourless ; nucleus band-like, much curved, 

 often forming an almost complete circle, situated in the anterior body- 

 half. Length of body 1/750 in. Hab. Attached to the gelatinous 

 tubules of Conoohilus volvox. 



A gathering made in the early part of the month of November 

 contained a large number of the beautiful free-swimming colonial 

 Rotifers Conocliilus volvoss, and every colony of the many examined 

 bore from three to six individuals of this parasite, or perhaps more 

 properly, commensal Vorticella, the pedicle being attached to the 

 gelatinous material which partially inclosed the colony. 



Vorticella molesta, sp. nov. 



Body conical- campanulate, less than twice as long as broad, soft 

 and changeable in shape, slightly constricted beneath the peristome, 

 the cuticular surface very finely striate transversely ; peristome ex- 

 ceeding the body centre in width, revolute ; pedicle stout, from five to 

 six times as long as the body, the muscular thread becoming rigid and 

 deeply chestnut brown in colour, presumably with age; contracted 

 body broadly obovate, the extremity of the pedicle invaginate. Length 

 of body, 1/375 in. Hab. Attached to the shell of an aquatic snail, 

 probably a young Lymnea. Social. 



The muscular thread of some species of Vorticella, notably of 

 V. picta, has been observed to contain many minute scarlet corpuscles, 

 and similar coloured particles have been noticed within or adherent to 

 the contractile filament of other forms ; but in the present species 

 the coloration is a deep chestnut brown extending evenly from the 

 point of attachment to the supporting object nearly up to the posterior 

 extremity of the body, gradually fading until the merest trace is 

 visible at the extreme anterior termination. No pedicle has been seen 

 with the colour reaching entirely up to the posterior border of the 

 zooid. The tint also extends to the sheath, but in a much less 

 marked degree. Those pedicles thus afi'ected had lost most of their 

 contractile power, only the proximal, almost colourless portion 

 retaining its ability to coil, an ability exercised imperfectly and 

 apparently with some difiiculty. The remaining or tinted region 

 presents the aspect of a shghtly undulate, rigid thread, this extended 

 and stiff condition remaining after the separation of the body and the 

 subsequent death of the muscle. The Vorticellse were infesting the 

 shell of the water snail to such an extent as to impede the progress of 

 the mollusc, and to give it the appearance of being surrounded by a 

 whitish fungoid growth. 



The transverse cuticular striae are very fine, requiring some 

 manipulation of the mirror to display them distinctly. 



