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CHAPTER VI. 



SYSTEMS OF CLASSIFICATION OF THE INFUSORIA ADOPTED BY VARIOUS 

 AUTHORITIES FROM THE TIME OF O. F. MULLER TO THE PRESENT DATE. 



CONSIDERABLE advantage being derived from an examination and compa- 

 rison of the various systems of taxonomy or classification that have at 

 different epochs been adopted with relation to the assemblage of organisms 

 described in this treatise, the more important are herewith submitted in 

 extenso. 



Commencing with the earliest essay at such systematic tabulation, as 

 included by O. F. M tiller in his ' Animalcula Infusoria ' published in the 

 year 1786, and reproduced at page 199, one is at once struck by the im- 

 portant influence that was exerted in its formulation by the then rudimen- 

 tary condition of the optical appliances at the disposal of this authority. 

 Thus, the entire series of seventeen genera embraced in his scheme are 

 separated into two leading groups or sections distinguished by their exhi- 

 bition or not of distinct locomotive appendages as viewed with the imperfect 

 microscopes of that day. It is now well known, however, that every one of 

 these, with the single exception of Proteus, possesses either well-developed 

 cilia or flagella. That exceptional type, with the five Mtillerian genera 

 Volvox, Vibrio, Gonium, Cercaria, and Brachionus, are necessarily eliminated 

 from the several classes and orders of the Infusoria as comprehended at the 

 present day, the remaining eleven, though considerably limited in their 

 significance, being still retained. The number of specific types included 

 in Miiller's system, deducting the Rotiferae, Phytozoa, and other extraneous 

 forms, closely approaches two hundred. 



With Ehrenberg's ' Die Infusionsthiere,' a far more extended series of 

 organisms, and corresponding elaboration of the classificatory system adopted 

 (see pages 200 and 201), is introduced. The supposed possession by all typical 

 Infusoria of a distinct oral aperture and numerous gastric cavities, is, as 

 stated in a previous chapter, the foundation-stone of his system, subordi- 

 nate to which the presence or, as in the case of Mtiller's system, presumed 

 absence of locomotive appendages, the character of these appendages, and 

 location of the oral and excretory apertures, receives attention. The 

 number of true infusorial forms included in Ehrenberg's magnificent treatise 

 may be set down as approximating three hundred and fifty, which are 

 included in sixteen family and eighty generic groups. 



Felix Dujardin's ' Histoire des Zoophytes Infusoires,' published in the 



O 2 



