228 Dr. C. F. J. Lachmann on the Organization of Infusoria. 



gelatinous matter for the purpose of forming sheaths, another 

 gelatinous exudation also occurs in a great many Infusoria, 

 which leads to the formation of a completely closed and generally 

 round case enclosing the animal which secretes it : this is the 

 cyst-formation, first described by Guanzati, and so often observed 

 of late, the object of which appears to be the protection of the 

 encysted animal from unfavourable circumstances in the water 

 inhabited by it, and from death by desiccation. How far en- 

 cystation is connected with reproduction, we shall see hereafter. 

 The cysts are not always smooth; thus Cienkowsky* saw Po- 

 dophrya fixa form transversely annulated cysts f and also de- 

 scribes other cysts with a stellate surface [Stylonychia pustulataX) ', 

 Stein observed longitudinally-ribbed cysts in Epistylis hranchio- 

 phila ; and I have seen finely-shagreened ones in a small undc- 

 scribed species of Epistylis. 



A nervous system has not yet been detected. Whether the 

 pigment-spots regarded by Ehrenberg in some Infusoria as eye- 

 spots, are really so, is uncertain ; a peculiar refractive body has 

 not yet been detected in them, whilst one occurs in the form of a 

 concavo-convex lens without a pigment-spot, close to the mouth, 

 in Bursaria flava, Ehrbg. Whether the clear bodies which 

 Ehrenberg supposed were to be regarded as ganglia in some 

 flagellated Infusoria, and the reniform bodies discovered by Stein 

 in the peristome of Opercularia articulata^ belong to a nervous 

 system, is still very problematical. 



With the exception of the cilia and other external appendages 

 of the body already mentioned, special organs of motion have 

 hardly yet been detected. Ehrenberg's account of muscular 

 strise giving origin to the series of cilia in many Infusoria is 

 not satisfactorily confirmed, and is regarded by most authors as 

 founded upon an illusion. The parenchyma of the body (not 

 the skin) of most Infusoria is contractile, although no one has 

 yet succeeded in distinguishing special muscles or muscular 

 layers. I have also been unsuccessful in my search for them ; 

 but, on the other hand, I was so fortunate, in common with my 

 friend, E. Claparede, as to observe an indubitable separate con- 

 tractile layer, in which longitudinal strise were generally to be 



* Siebold and KoUiker's Zeitschr. vi. p. 302, and Bull, de I'Acad. Tra- 

 periale de St. Petersb. 1855, p. 297. 



t Stein regarded these cysts as transition steps between Vorticella mi- 

 crostoma and Podophryafixa, and thought that they were produced by the 

 encystation of the former, and not of the latter. Weisse described them 

 (Bull. Acad. St. Petersb.) as independent Infusoria, under the name of 

 Orcula trochus. 



X I have also seen these cysts, and think that they are what Weisse has 

 described (Bulletin, &c.) under the name of Discodella multipes. 



§ hoc. cit. p. 117- 



