Dr. C. F. J. Lachmann on the Organization of Infusoria, 119 



tractile stem, and the species of Epistylis and Trichodina^) 

 the longitudinal axis of the vestibulum and oesophagus runs 

 tolerably parallel to the plane of the ciliary disk, whilst that of 

 the pharynx has rather the direction of the axis of the body. 

 In these, therefore, the axis of the ciliary spiral, which is con- 

 tinued as far as the pharynx, changes its direction at the com- 

 mencement of the vestibulum : whilst it coincided with the axis of 

 the body outside the vestibulum, it stands almost perpendicular to 

 it within the vestibulum and in the oesophagus. In the very 

 elongated forms of the OphrydincBj Ehrbg., which inhabit sheaths 

 [OphrydiuiUj Vaginicola, Cothurniaf), the longitudinal axis of 

 the vestibulum and oesophagus coincides more with that of the 

 body, as also in the genus Opercularia (as circumscribed by 

 Stein) and Lagenophrys, Stein ; in the two latter the vestibulum 

 is very wide, whilst in the elongated species it is narrow, but 

 generally possesses a deep excavation for the anus. 



The portion of the ciliary spiral which is situated outside the 

 vestibulum is not of equal length in all Vorticellince : in many 

 {Forticella, Carchesium, Zoothamnium, Scyphidiaj TrichodinaX, 



* Trichodinapediculus, Ehrbg. and T. mitra, Siebold. The other species 

 of Ehrenberg's genus — Trichodina grandineUa {Halteria yrandinella, 

 Duj.), tentaculata and vorax, — are not VorticellincB, and this is also the 

 case with Urocentrum. On the other hand, Dujardin's genus Scyphidia 

 approaches this group of the VorticellincB ; it was founded by him for the 

 sessile, stemless forms, without a carapace. It is true that all the species 

 described by him and Perty as belonging to this genus are to be removed 

 from it, as they have a short stem, and only appear to be particular states 

 of pedunculate VorticellincB, in which the stem has not attained its usual 

 length ; but on the other hand two other species must be included in it, 

 both of which attach themselves to the naked parts of small freshwater 

 Mollusca, and never form a stem, but which were often observed by me in 

 process of division, and are easily distinguished from other forms, which 

 are also attached at first, by their posteriorly-truncated form and a pro- 

 jecting pad at the margin of the hinder end. The Sc. limacina ( Vorti- 

 cella limacina, O. F. Miiller) lives on small species of Planorbis. The 

 body is nearly cylindrical, tapering a little at each end, and annulated ; 

 the peristome is narrow and not turned backwards ; the ciliary disk ia 

 narrow and furnished with a projecting umbilicus in the middle, and the 

 posterior truncated surface is provided with a thick pad-like margin. 

 Length of the animal ^V-g^o^"'. The second species, Sc.physarum, Lachmann, 

 lives on the naked parts of species of Fhysa. It is longer and more uni- 

 formly cylindrical than the preceding ; the peristome is longer and often 

 turned backwards, and the hinder margin is thinner and shorter. 



t The genus Tintinnus, of which, in company with M. E. Claparede, I 

 observed many species on the Norwegian coast, is ciliated all round, and 

 differs so greatly in the alimentary apparatus from the VorticellincB, that 

 it is impossible for it to remain in the same family. A species inhabiting a 

 gelatinous sheath occurs also in the freshwater in the Thiergarten at Berlin. 



X The most recent describer of Tr. pediculus mentions the existence of 

 a ciliary spiral leading to the mouth : Stein regarded this as a circle. — 

 Miiller's Archiv, 1855, p. 357. 



