Chapter 30 

 Subclass 2 Euciliata Metcalf 



THE most conspicuous group of Protozoa containing 2 nuclei : 

 macronucleus and micronucleus. Sexual reproduction is 

 through conjugation. We owe Kahl a great deal for his series of 

 comprehensive taxonomic studies of free-living ciliates. The eucil- 

 iates are grouped under the following four orders : 



Without adoral zone of membranellae Order 1 Holotricha 



With adoral zone of membranellae 



Adoral zone winds clockwise to cytostome 



Peristome not extending beyond general bod}^ surface 



Order 2 Spirotricha (p. 573) 



Peristome extending out like funnel 



Order 3 Chonotricha (p. 614) 



Adoral zone winds counter-clockwise to cytostome 



Order 4 Peritricha (p. 616) 



Order 1 Holotricha Stein 



The members of this order show uniform ciliation over the en- 

 tire body surface. Adoral zone does not occur. The majority possess 

 a cytostome, which varies among different forms. Nutrition is holo- 

 zoic or saprozoic. Asexual reproduction is usually by transverse 

 fission and sexual reproduction by conjugation. Encystment is 

 common. The holotrichous ciliates are parasites or free-living in 

 all sorts of fresh, brackish, and salt waters. 

 The order is here divided into 6 suborders : 



Without cytostome Suborder 1 Astomata (p. 488) 



With cytostome 



Cytostome not rosette-like 



Without special thigmotactic ciliated field 



Cytostome on body surface or in peristome, without strong cilia 



Suborder 2 Gymnostomata (p. 496) 



Cystome in peristome, bearing special cilia or membranes 



Peristome lined with rows of free cilia 



Suborder 3 Trichostomata (p. 531) 



Peristome with membrane; with or without free cilia 



Suborder 4 Hymenostomata (p. 547) 



With well-developed thigmotactic ciliated field; commensals in 



mussels Suborder 5 Thigmotricha (p. 560) 



Cytostome rosette-like small aperture or obscure; endoparasitic. . . 

 Suborder 6 Apostomea (p. 567) 



487 



