T 



CHAPTER XXVIII 



SUBCLASS 2 EUCILIATA METCALF 



HE EUCILIATA are subdivided into five orders according 

 to the arrangement of the cilia, cirri, and adoral zone: 



Without adoral zone Order 1 Holotrichida 



With adoral zone 



Adoral zone turns to left 



Cilia over the entire body Order 2 Heterotrichida 



Cilia on body absent or a few Order 3 Oligotrichida 



Cilia or cirri on the ventral side only Order 4 Hypotrichida 



Adoral zone turns to right Order 5 Peritrichida 



ORDER 1 HOLOTRICHIDA STEIN 



The members of this order possess cilia which are uniformly 

 distributed over the entire body surface. A cytostome may or 

 may not be present. Adoral zone is never present. The position 

 of the cytostome varies among different forms. In connection 

 with the cytostome, there may be a proboscis in some forms 

 and in one group the so-called pharyngeal apparatus may 

 be well developed. Mode of nutrition is holozoic or parasitic. 

 Asexual reproduction is usually by transverse fission. Sexual 

 reproduction is ordinarily isogamous conjugation. Encystment 

 is common. These Euciliata are parasites or free-living in all 

 sorts of freshwater body and less frequently in marine water. 



The order is here divided into three suborders. 



Without cytostome Suborder 1 Astomina 



With cytostome 



Cytostome usually closed; oral membrane absent 



Suborder 2 Gymnostomina 



Cytostome usually opened; oral membrane present 



Suborder 3 Trichostomina 



Suborder 1 Astomina Cepede 



Genus Rhizocaryum Caullery and Mesnil. One species, R. 

 concavum (Fig. 146, a), an intestinal inhabitant of the marine 



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