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CHAPTER VII. 



SYSTEMATIC DESCRIPTION OF THE INFUSORIA FLAGELLATA. 



Class I. FLA GELLA TA . 



ANIMALCULES bearing one, two, or more long, lash-like flagella, which 

 mostly represent the sole organs of progression, but are occasionally 

 supplemented by cilia, pseudopodia, or other locomotive or prehensile 

 appendages. Oral or ingestive system varying in character ; definite, diffuse, 

 or indistinct. One or more contractile vesicles almost invariably represented. 

 Multiplying rapidly by binary fission and by the subdivision of their entire 

 body-mass into sporular elements. The sporular reproductive process 

 often preceded by the complete fusion or conjugation of two or more adult 

 zooids. 



The title of the Flagellata, as distinctive of a large and important series of infu- 

 sorial types, was employed almost simultaneously by Johannes Miiller and F. Cohn 

 about the year 1853 ; it is practically synonymous with that of the Filigera introduced 

 one year previously by M. Perty, and with the Mastigophora of R. M. Diesing. 



Although thus receiving their characteristic name at a comparatively recent date, 

 the members of this class were known to the majority of the earlier writers, being 

 abundantly figured and described in the works of O. F. Miiller, and C. G. Ehrenberg, 

 while a first intelligible record of their existence is undoubtedly contained in 

 Mr. John Harris's account of little fish-like animals (Euglena viridis) communicated 

 to the ' Philosophical Transactions ' for the year 1696, reproduced at pages 9 and 

 10. By these earlier authorities, however, the flagelliform organs were almost 

 altogether overlooked, and it was not until the employment of more perfected 

 instruments having a comparatively high magnifying power, at the hands of 

 Felix Dujardin and Maximilian Perty, that these appendages were extensively 

 recognized as representing the essential organs of locomotion, or their number, 

 character, and mode of insertion made use of for the purpose of generic diagnosis. 

 Much even then remained to be discovered with relation to their more minute 

 organization. While Ehrenberg had declared that all these flagellate organisms 

 possessed a distinct mouth, and in most instances numerous gastric cavities, 

 Dujardin made the entire absence of an oral aperture a leading distinction of the 

 Order III. or Flagelliferous section of his ' Zoophytes Infusoires.' So much 

 uncertainty has prevailed, again, respecting the claims of the Flagellata for recogni- 

 tion as animal organisms their external shape and mode of locomotion correspond- 

 ing so closely with those of many undoubted unicellular plants or Protophytes, and 

 with the spermatic elements, " antherozooids " or " zoospores," of the higher Crypto- 

 gamia that almost down to the present time biologists have refused to admit them 

 among the ranks of the typical Infusoria. The more perfect insight into the structure 

 and life-history of the representatives of this class, obtained by the assistance of the 

 higher magnifying glasses of recent construction, has, however, practically revealed 

 in them the existence of an entirely new world of mieroscopic organisms, possessing 

 the most evident animal attributes, and exhibiting with relation to each other an even 



