Chapter 31 

 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 comprehen- 

 sive taxonomic studies of free-living ciliates. The euciliates 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 body surface 



Order 2 Spirotricha (p. 636) 



Peristome extending out like funnel. . . . Order 3 Chonotricha (p. 681) 



Adoral zone winds counter-clockwise to cytostome 



, Order 4 Peritricha (p. 683) 



Order 1 Holotricha Stein 



The members of this order show uniform ciliation over the entire 

 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 com- 

 mon. The holotrichous ciliates are conspicuous free-living forms in all 

 sorts of fresh, brackish, and salt waters, though some are parasitic. 



The order is here divided into 6 suborders: 



Without cytostome Suborder 1 Astomata (p. 552) 



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. 560) 



Cystome in peristome, bearing special cilia or membranes 



Peristome lined with rows of free cilia 



Suborder 3 Trichostomata (p. 593) 



Peristome with membrane; with or without free cilia 



Suborder 4 Hymenostomata (p. 608) 



With well-developed thigmotactic ciliated field; commensals in mus- 

 sels Suborder 5 Thigmotricha (p. 623) 



Cytostome small rosette-like aperture or obscure ; parasitic 



Suborder 6 Apostomea (p. 630) 



551 



