680 ORDER PERITRICHA. 



the peristome-border dilated, but not crateriform or greatly revolute, a 

 deep notch or constriction usually separating it from the remainder of the 

 body ; oral fossa large, pharynx deeply prolonged ; the posterior extremity 

 of the body, immediately preceding its junction with the pedicle, conical 

 and attenuate ; pedicle transparent, slender, three or four times longer than 

 the body, mostly assuming in connection with this structure a more or less 

 inclined position ; parenchyma transparent or pale yellow, finely granulate. 

 Length 1-430" to 1-300". HAB. Fresh water, social. 



This species, originally described by O. F. Miiller, and since lost sight of, has 

 been re-discovered by De Fromentel, and has more recently, February 1879, been 

 met with in some abundance by the author in the neighbourhood of St. Heliers, 

 Jersey. The distinctive feature by which it may be readily identified, is afforded by 

 the gracefully inclined or pendulous position almost invariably assumed by the broad 

 campanulate body with reference to its supporting pedicle. The pedicle itself, 

 again, when the zooid is fully expanded, frequently remains curved, and on con- 

 traction assumes a more or less loose and imperfect spiral coil. The substance of 

 the body and overlying cuticle is soft and plastic, permitting of a considerable 

 puckering of the contour of the periphery, but this to a much less degree than is 

 observable in either Vorticella campanula or V. citrina. 



The majority of the examples examined exhibited a pale yellowish hue, and were 

 found both solitary and forming small scattered colonies, attached to Conferva taken 

 from a roadside ditch, containing much decaying vegetable matter, running during 

 the winter months, but habitually dry in summer. These specimens were found to 

 live for a long while in the close confinement of a small glass vessel. In his list of 

 synonyms, De Fromentel has proposed to identify this type with the Vorticella 

 infusionum of Dujardin, a species, however, with which it certainly cannot be said to 

 exhibit a single point in common. The marine Vorticella gemella of O. F. Miiller 

 would appear to be a type closely corresponding with the present type, if not 

 indeed a merely salt-water variety of it. In many cases the presence of two zooids 

 upon one stalk, resulting from longitudinal fission, was noted by that early- inves- 

 tigator, and being interpreted by him as the normal expression of the species, 

 suggested the title given. 



Vorticella aperta, From. PL. XLIX. FIG. 17. 



Body conical-campanulate, or pyriform, one and a quarter times longer 

 than wide, tapering posteriorly, slightly constricted beneath the peristome ; 

 surface smooth and transparent ; the substance of the inner layer of the 

 body contracted at its junction with the pedicle, and presenting the appear- 

 ance of a supplementary thick bounding membrane or cortical layer around 

 this point ; pedicle stout, about three times longer than the body. Length 

 1-400". HAB. Fresh water. 



Vorticella procumbens, From. PL. XLIX. FIG. 18. 



Animalcules exceedingly transparent, campanulate, scarcely longer than 

 broad ; peristome everted ; pharyngeal cleft much prolonged ; pedicle 

 decumbent, three or four times longer than the body. Length 1-530". 



HAB. Fresh water. 



The most important character of this species, as described by De Fromentel, is 

 the procumbent position always assumed by the pedicle when in a state of full 

 extension. 



