52 ORGANIZATION OF THE INFUSORIA. 



comparatively complex type of structure altogether at variance with the 

 foregoing unicellular conception. Enumerated in chronological order, the 

 first interpretation attributing a complex and multicellular structural type 

 to these organisms was advanced by C. G. Ehrenberg, who in the year 

 1830 enunciated his celebrated Polygastric theory. In accordance with 

 Ehrenberg's interpretation, the Infusoria, including both the simpler Flagel- 

 late and more highly differentiated Ciliate representatives of the series, 

 were, as previously stated, distinguished by the possession of a variable 

 number of distinct stomach-cavities, and of glandular and sensory organs 

 of various descriptions, the affinities of the group as a whole being deemed 

 by him as most nearly approximate to that of the Annelida. Founding 

 their arguments upon a basis altogether independent of Ehrenberg's 

 remarkable hypothesis, several authorities have since held the Ciliate 

 division of the Infusoria to exhibit similar affinities with the lower or Tur- 

 bellarian worms, the names of Oscar Schmidt and Diesing being most 

 eminently conspicuous in this direction. According to the views of the 

 last-named taxonomist, however, the Peritrichous group of the Ciliata 

 exhibited a type of structure more nearly approaching that of the Polyzoa, 

 Diesing's interpretation in this connection being likewise independently 

 maintained by the elder Agassiz. The most powerful opposition to the 

 unicellular nature of the Infusoria, such opposition being based upon the 

 supposed nearer conformance of their structure to that of the Coelenterata 

 or zoophytes, is undoubtedly found in the conjoint writings of Claparede 

 and Lachmann. A corresponding Ccelenterate interpretation of the affinities 

 of this group, as illustrated more especially by the organization of the Vorti- 

 cellidse, has been quite recently advocated by Richard Grecff. 



Among those authorities who, while contesting the unicellular nature of 

 the Infusoria as advocated by Von Siebold, have substituted for it no definite 

 and compensating alternative interpretation, may be mentioned the names 

 of Perty, Lieberkuhn, and to a considerable extent also Stein. The crucial 

 test respecting the disputed unicellular or multicellular structure of the 

 infusorial body is undoubtedly, however, to be found associated with the 

 phenomena of development. As pointed out more especially by Professor 

 Haeckel in his ' Morphologic der Infusorien,' published in the year 1873, the 

 entire life-history of an Infusorium, taken even in its most exalted grade of 

 development, as represented by the higher Ciliata, is an epitomization only 

 of the life-history of a simple cell. By the various modes of fission or 

 duplicative division common to all representatives of the class, the infusorial 

 zooid multiplies itself in a manner precisely corresponding with what obtains 

 in the augmentation of the ultimate elements of all cellular structures. 

 Again, in those more rarely observed, but still very generally occurring 

 phenomena of sporular or internal gemmule-production, the sporoid body 

 or embryo commences life as an undoubted simple cell, and retains this 

 same morphological simplicity for the remainder of its existence. At 

 no epoch of its history, from its pristine germination to its ultimate 



