Rotatoria.'] infusorial animalcules. 605 



The above characters are according to Ehrenberg. With regard 

 to the affinities of the class with respect to other groups of the 

 animal kingdom, the reader is referred to Part I. of this Work ; but, 

 it may be remarked that Professor Owen considers the members of 

 this class have the strongest affinity with the Crustacea, and con- 

 sequently belong to the Province Articulata, occupying a higher 

 position than Radiata and Entozoa. On the other side, the Rotatoria 

 has the nearest affinity with the Polygastrica through the Vorticella 

 family. 



Siebold adopts the classification of Ehrenberg for the Rotatoria, 

 omitting, however, a few genera. Dujardin, on the contrary, regards 

 the principles employed by Ehrenberg in framing his division of 

 these animals as faulty and uncertain, and consequently puts 

 forward one of his own. But he includes among his Systolides, 

 for so he calls the Rotatoria, the curious animals named Tardigrada, 

 which, although having some affinity with the true Rotatoria, are so 

 wanting in all the essential characteristics of the latter, that no 

 naturalist now thinks of associating the two together. Indeed at 

 the time of publishing his book, Dujardin himself expressed doubts 

 as to so placing them. 



To resume, however, Dujardin formed four grand divisions of the 

 Rotatoria, Viz. 1. Those which live fixed by their posterior extremity. 

 2. Those which have but one mode of locomotion by means of their 

 vibratile cilia, and are always swimmers, 3. Those which exhibit 

 two modes of progression by crawling after the manner of leeches, 

 and by swimming. 4. Those which creep by uncini, and are 

 destitute of vibratile cilia. 



This last division is constituted by the Tardigrades ; the third 

 comprises only the Rotifera : the first includes but two families, 

 the Flosculariens and Melicertiens, whilst the second contains by 

 far the largest number, which are distributed under two sections, 

 according as the integument is flexible throughout, or in part solid, 

 or otherwise constitutes a shield. 



The last section so characterised is made up of the Brachioniens, 

 and of the less characteristic families, Polyai'thra, Rattula. The 

 soft-skinned Systolides are represented in the families Furcidariens 

 and Albertiens. 



