240 Dr. C. F. J. Lachraann on the Organisation of Infusoria. 



point is formed by the contractile vesicle, is contained in the 

 parenchyma of the body of all ; that, besides fissation and gem- 

 mation, they possess another mode of reproduction, in which 

 small embryos are formed in the nucleus, but that an alterna- 

 tion of generations has never been detected in the Infusoria; 

 and, lastly, that Stein's view of the connexion of the Vorticella 

 and AcinetcB is an unfounded and improbable hypothesis. 



EXPLANATION OF PLATE IX. 



All the figures, with the exception of fig. 8, are magnified about 300 

 diameters. The lettering of the separate parts is, as far as possible, the 

 same in all the figures ; so that a, a indicates the peristome ; b, the com- 

 mencement of the series of cilia leading to the mouth ; c, d, in the Vorti- 

 cella, the entrance mto the vestibulum, which lies between c, d and e, f; 

 e, the anus ; f, the mouth ; g, the outer extremity of the bristle situated 

 in the vestibulum ; h, or /, h, the oesophagus ; h, i, the pharynx ; and k, 

 the contractile vesicle. 



Fiffs. 1-5. VorticelliiKB. Of the cilia of the outer series, only those which 

 are visible at the margin of the figure are indicated. 



Fig. 1. Vorticella campanula, seen from the ventral side. At e we see 

 through the mouth into the lumen of the oesophagus ; the pha- 

 rynx is not visible in this position ; of the stronger cilia situated 

 in front of the mouth, only one is represented. The pale curved 

 body represents the nucleus. 



Fig. 2. Vorticella nehdifera, inflated and dying, so that the peristome is 

 obliterated. The portion of the ciliary spiral which is situated 

 on the back of the animal is only indicated by a dotted line. 



Fig. 3. Carchesium polypinum, seen from the front directly upon the ciliary 

 disk ; the ciliary spiral is only indicated by a dotted line. The 

 pharynx is only seen in section : k represents the section of the 

 process running from the contractile vesicle towards the ciliary 

 disk. 



Fig. 4. Opercularia berberina, Stein, seen from the back. The portion of 

 the ciliary spiral situated in the vestibulum is only indicated by a 

 line. At /, in this and the following figure, a still fusiform morsel 

 is represented. The pale body to the left above h represents a 

 section of the nucleus. 



Fig. 5. Scyphidia limacina, Lachm. By mistake, the cilia are not repre- 

 sented on the extreme margin of the ciliary disk, as they should be. 



Figs. 6, 7- Chcetospira Mulleri, Lachm., sitting in its sheath, n. Of the 

 fine cilia covering the whole body, a few are represented only in 

 fig. 6. 



Fig. 6. A rotating animal. At m is a ball of excrement on its way to the 

 anus. 



Fig. 7- An animal only just extended, and not rotating. 



Fig. 8. Stentor polymorphus, not much magnified. On the right side the 

 contractile vesicle, k, is seen, with the lateral vessel, exhibiting 

 various inflations, running backward ; o, o are the two dilatations 

 of the annular vessel. The anus, e, lies on the dorsal surface, 

 which is turned from the observer. 



Fig. 9 shows a section through the posterior extremity of a Stentor. The 

 thin, pale, outermost portion represents the skin bearing the cilia 

 and hairs ; and the darker portion, situated more internally, the 



