452 GENEKAL CHARACTERS OF INFUSORIA. 



the ciliated lobes are so formed as not to bear the least resemblance 

 to wheels. In their general organization, these ' Wheel-animal- 

 cules' must certainly be considered as members of the Articulated 

 division of the Animal Kingdom ; and they seem to constitute a 

 class in that lower portion of it, to which the designation Woi-ms 

 is now commonly given. — Notwithstanding this wide zoological 

 separation between these two kinds of Animalcules, it seems most 

 suitable to the plan of the present work to treat of them in con- 

 nection with one another ; since the Microscopist continually finds 

 them associated together, and almost necessarily ranges them in 

 his own mind under one and the same category. 



338. Infusoria. — This term, as now limited by the separation 

 of the Rotifera, is applied to a far smaller range of forms than that 

 which was included by Prof. Ehrenberg under the name of ' poly- 

 gastric ' animalcules. For a large section of these, including the 

 Desmidiacece, Diatomacece, Volvocinece, and many other Proto- 

 phytes, have been transferred by the almost concurrent voice of 

 those Naturalists whose judgment is most to be relied-on, to the 

 Vegetable Kingdom. The Rhizopod group, again, must be ex- 

 cluded, as being very distinct in its plan of organization from the 

 true Infusoria. And, lastly, it is not impossible that many of the 

 reputed Infusoria may be but larval forms of higher organisms, 

 instead of being themselves complete animals. Still an extensive 

 group remains, of which no other account can at present be given, 

 than that the beings of which it is composed go through the whole 

 of their lives, so far as we are acquainted with them, in a grade 

 of existence which is essentially ' protozoic ;' their lowest forms 

 approximating closely to the highest Rhizopods, whilst even in 

 their most elevated types we find no such differentiation of parts 

 as would justify our associating them with any other class. — Pass- 

 ing by the descriptions of Prof. Ehrenberg as no longer authori- 

 tative, the following general account of the organization of In- 

 fasoria is given in accordance with the concurrent representations 

 of the best observers of the present time. 



339. The bodies of Infusoria consist of Sarcode, of which the 

 outer layer possesses considerably more consistence than the internal 

 portion : the process of differentiation having here advanced suffi- 

 ciently far to establish a clear distinction between the Ectosarc 

 and the Endosarc. Sometimes, as in Paramecium, a distinct 

 pellicle may be recognized on the surface of the Ectosarc or 

 'cortical layer' of the body ; and this pellicle, which is studded with 

 regularly-arranged markings like those of Diatomacese, seems to be 

 the representative of the carapace of Arcella, &c. (§ 333), as of the 

 cellulose coat of Protophytes. In certain Infusoria, as Paramecium 

 (Loxodes) bursaria, the surface of the body is beset with ' tricho- 

 cysts' resembling those of Zoophytes in miniature (§ 428) ; but 

 it is remarkable that these are not present in all the individuals 

 of the species in which they occur. Sometimes, again, the tegu- 



