INFUSORIAL ANIMALCULES. 31 



One great change agreed upon by those who dissent from the 

 Berlin Professor, is the cxchision of the DesimidiecG and JDiatomece 

 from the true animalcules, and the elevation of the Rotatoria to a 

 position in the animal scale much higher than the so-called Polygas- 

 trica, with which their elaborate organization forbids theii' associa- 

 tion imdcr the common name of Infusoria. 



In the classification appended, proposed by Siebold (Section XVII.) 

 it will be seen that the term Infusoria is restricted to animals 

 evidently moved by cilia, whereby not only the Bacillaria, but also 

 those animalcules moving by variable processes under the title of 

 Rhizopodes, ai-e separated from Infusoria. In Dujardin's system, the 

 Rhizopoda are, however, classed -wdth Infusoria. 



Section XII. — Of the Polygastrica, as a class, and of their hahitats 

 emd movetnmts. — Though some portions of the system of classification 

 devised by Ehrenberg are certainly objectionable, I still feel that an 

 arrangement is yet to be discovered that Tvill supersede it. 



In the opinion of the great Berlin naturalist, the Polygastrica con- 

 stitute a natm'al group of animals, and are as satisfactorily distinguished 

 as any other class. In this \dew, no other naturalist entirely coin- 

 cides : almost all exclude the Bacillaria and Closterina (f. e. the 

 BiatomecB and Besmidiem) from the Polygastrica ; many go still 

 fui'ther, and declare this class to be a collection of heterogeneous 

 beings, many of which do not even belong to the animal kingdom. 

 Thus, M. Agassiz says (Annals of Xatiu-al History, vol vi, 1850, p. 

 156), ''Eecent investigations, upon the so-called Anentera, have 

 satisfactorily shown, in my opinion and in that of most competent 

 obseiwers, that this tj-pe of Ehrenberg' s Polygastrica, without gastric 

 cavities, and without an alimentary tube, are really plants belonging 

 to the order of Algae in the widest extension of this group ; whUe 

 most of the monad tribe are merely moveable germs of various kinds 



of other Algae. As for the Enter odela most of them, far from 



being perfect animals, are only germs in an early stage of development. 

 The family of Vorticella exhibits so close a relation with the Bryozoa 

 (cilio brachiate polj-jies), and especially with the genus PedicelUna, 

 that I have no doubt that wherever Bryozoa should be placed, Vorti- 

 cella should follow, and be ranked in the same division with them. 



The last group of Infusoria, Bursaria, Paramecium, and the like, 



