CHAPTER VI 



PROTOZOA {CONTINUED) : INFUSORIA (CILIATA AND SUCTORIA) 



IV. Infusoria. 



Complex Protozoa, never holophytic save by symbiosis ivith plant 

 commensals, never amoeboid, with at some 'period numerous short 

 cilia, of definite outline, ivith a double nuclear apparatus con- 

 sisting of a large meganucleus and a small micronucleus (or 

 several)} the latter alone taking part in conjugation (karyo- 

 gamy), and giving rise after conjugation to the new nuclear 

 apparatus. 



The name Infusoria was formerly applied to the majority of 

 the Protozoa, and included even the Eotifers. For the word 

 signifies organisms found in " infusions " of organic materials, 

 including macerations. Such were made with the most varied 

 ingredients, pepper and hay being perhaps the favourites. They 

 were left for varying periods exposed to the air, to allow the 

 organisms to develop therein, and were then examined under the 

 microscope. 2 With the progress of our knowledge, group after 

 group was split off from the old assemblage until only the ciliate 

 or flagellate forms were left. The recognition of the claims of 

 the Flagellates to independent treatment left the group more 

 natural ; 3 while it was enlarged by the admission of the Acinetans 

 (Suctoria), which had for some time been regarded as a division 

 of the Ehizopoda. 



1 On this account Hickson has termed the group "Heterokaryota" in Lankester's 

 Treat. Zool. i. fasc. 1, 1903. 



2 See Baker, Employment for the Microscope, ed. 2, 1758. 



Saville Kent's valuable Manual of the Infusoria (1880-1882), which gives 

 figures of every genus and descriptions of every species known at that date, includes 

 the Flagellates in its scope. 



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