Dr. C. F. J. Lachmann on the Organizatiori of Infusoria. 119 



tractile stein^ 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 dn-ection 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 Ophrydince, Ehrbg., which inhabit sheaths 

 {Ophrydiuin, Vayinicola, Cothurniaf), the longitudinal axis of 

 the vestibulum and oesophagus coincides more with that of the 

 body, as also iu the genus Operculuria (as circumscribed by 

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

 is very wide, whilst iu 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 Vorticellina : in many 

 ( Vorticella, Carchesium, Zouthamnium, Scyphidia, Trichodina %, 



* Trichodina pediculus, Ehrbg. and T. mifra, Siebold. The other species 

 of Ehrenberg's genus — Trichodina grandinplla {Hulteria grandinella, 

 Duj.), teiitaculata and vorax, — are not Vorticdlince, and this is also the 

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

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

 sessile, stemless forms, without a carajjace. It is true that all the sjjeeies 

 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 jiedunculate Vurticcllina;, 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 themseh'cs to the naked parts of small freshwater 

 MoUusca, 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 attacheil 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 is 

 narrow and furnished with a jjrojecting umbdicus in the middle, and the 

 posterior truncated surface is j)rovided with a thick pad-like margin. 

 Length of the animal ^'^"a'o"'- The second species, Scpht/sarum, Lachmann, 

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

 formly cylindrical than the jircceding ; tiie peristome is longer and often 

 turned backwards, and the lunder 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 Vorticellincp, 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 tlescriber 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. 



