642 



SYSTEMATIC HISTORY OF THE INFUSORIA. 



under surfaces. Mouth a rather curved 

 and ciliated fissure. Cilia very fine, 

 those of the upper surface the more di- 

 stinct, although faint. Small specimens 

 are colourless and transparent ; but larger 

 ones have dark grey molecules or chloro- 

 phyll within. Movements tolerably ac- 

 tive. Pei-tj^ once thought this species 

 and Traclielius strictus (Duj.) to be young 

 individuals of Spirostomum, but he subse- 

 quently found examples 1-84" in length. 



O. galUna (Perty) = Trichoda gallina 

 (?) (Miiller). — Anterior portion hyaline, 

 flat, with laT'ge cilia; molecules grey. 

 Only once seen. 



O. decmnana (Perty). — Outline rather 

 irregular; rather smaller in front than 



behind, broadest in the middle; ends 

 rounded ; upper suiface slightly convex, 

 lower flat. Mouth wide. It differs in 

 size from O. platy stoma and in its out- 

 line both fi'om that species and O. fiisca. 

 In length it equals TJrostyla grandis, but 

 is much broader. Bern, in ponds. 1-96". 

 O. fiisca. — Narrow, elliptical, upper 

 sm-face convex, lower concave. Oral 

 orifice wide. Colour usually yello^dsh 

 or blackish-browTi. Lives in stagnant 

 and mouldy water. Cilia in fi'ont and 

 about the mouth strongest ; but no uncini 

 occm- there. TJrostyla grandis differs 

 fi'om it by the uncini on its border. 

 1-160" to 1-84". 



Genus CEEATIDIUM (XXV. 338, 339).— Ciliated, with horns on the 

 frontal region, but no styles or uncini. Little of their organization is known ; 

 and therefore their systematic position is uncertain. A power of not less 

 than 350 diameters is required to examine these creatures. 



Ceeatidium cuneatum (xxv. 338, 

 339). — Body triangular ; front trimcated, 

 as also the two horns ; upper side smooth. 

 Ehrenberg found this whitish animalcule 

 in 1820, amongst Confervae, but had not 



lately seen it. Dujardin believes it to 

 have been a mutilated Oxytricha. It 

 vibrates, runs, and climbs quickly. 

 1-430". 



Genus KEHOISTA (XXY. 340, 341).— Cilia and uncini present, but no 

 styles. Body soft, flexible, oval, flattened, and ciliated, with claws (uncini), 

 and perhaps setae, on the under siufaee. Yacuoles numerous ; the oral (and 

 probably the anal) aperture is upon the ventral surface. One or more con- 

 tractile vesicles and a nucleus have been seen; but self-division has not 

 been observed. 



This genus, instituted by Miiller, was at first adopted by Ehrenberg with 

 little modification ; but subsequently he transposed almost all its species to 

 his genus Stylonychia, on account of their possessing styles as well as uncini. 

 This can scarcely be considered a sufiiicient reason for the construction of a 

 new genus; and accordingly Dujardin rejects Sfylonychia, and thus restores 

 the genus Kerona nearly to its original importance. As already noted, he 

 likewise adopts Kerona as the representative of his family Keronina. Perty 

 coincides with the French naturalist, and rejects both Ceratidium and Stylo- 

 nychia, treating the species of the latter as examples of Kerona. He remarks 

 that Ehrenberg has very needlessly changed the name Kerona, given by MiiUer, 

 for that of Stylonychia. 



The Keronce, thus understood, differ from Oxytricha only ii^ the form of 

 their ciiThi or processes, the base of which is commonly dilated in the form 

 of a transparent globe, and moveable withal. Moreover they are equally 

 voracious, are abundant in stagnant water and infusions, and capable of 

 being much varied in form. 



Kerona polyporwn. — Whitish, de- 

 pressed, elliptical, and renifonn ; a series 

 of cilia suiTounds the frontal region, ex- 

 tended from beneath the mouth. Ehren- 

 berg counted above forty vacuoles, many 

 of them filled ^nXh. brownish (half- 



digested green) Monads, (xxv. 340 is 

 a back \dew, and 341 a side view, 

 climbing.) Parasitic on Hydra vulgaris 

 (Microsco^nc Cabinet, p. 7). Animals 

 infested with them die. 1-144". 

 This species is thet^-pe of a genus named 



