3(> GENEEAL HISTOBY OF 



tions, up to the present day (in England at least), professing to give 

 on account of Dr. E.'s classification, his older, and I may say, 

 abandoned systems, have alone been presented. 



Ehrenberg, in his great work entitled Die Infusionsthierchen, has 

 not devoted much space in defining the Infusoria, or in. giving a 

 general view of the subject ; but he commences almost immediately 

 with their systematic arrangement; hence the Third Part of this 

 work will give the reader some idea of the general character of that 

 splendid volume ; though the design of the two differing, namely, the 

 latter being a work of reference, this a manual, many alterations, 

 omissions, and additions have been made, especially in the present 

 edition ; hence it will be alike unjust to that distinguished natu- 

 ralist, as to myself, to consider the one a mere abstract of the other. 



Should the reader possess a copy of my first distinct work on this 

 subject — the NftturallTtsiori/ of Aninialciiles, and will make a general 

 comparison between the system adopted in that work, and that in 

 the present, he cannot fail to observe that, although the principles 

 of classification of Mviller and Ehrenberg are widely different, yet 

 many of the groups occupy similar positions in the two systems. 

 This coincidence is especially striking in the case of the Vibrio of 

 Miiller and the BacUlaria of Ehrenberg, and also between the com- 

 mencing and concluding genera in each arrangement. 



To proceed : Professor Ehrenberg di^ddes the Infusoria into two 

 gi-and classes — the Polygastrica and the Rotatoria : the fonner so- 

 called by reason of the fimetion of digestion, being carried on by 

 numerous globular vesicles, or stomachs, whilst the latter, like most 

 higher animals, have only one stomach. 



Each class is again subdi\"ided into families and genera, which are 

 presented ia a tabular form; and further details concerning the 

 grouping of the Pohjgastrica, by Ehrenberg, are given in the section 

 devoted to the consideration of theh* classification. 



Based as the system of Ehrenberg is, on a particiilar hypothesis of 

 the organization of Infusoria, of coiu-se it can be accepted only by 

 those who subscribe to that hj-pothesis. Hence Siebold, Dujardin, 

 and others, who cannot accept the polygastric sti'ucture as a fact, 

 seek for some arrangement in accordance with their own ^iews of 

 animalcular organization (see Section XIII.) 



