8 INFUSORIA. 



Order 2. Ciliata ( = Infusoria in limited sense). Protozoans of stable 

 form, with firm ectosarc (cortical layer), giving origin to variously dis- 

 posed cilia which pierce the cuticle when present. Usually possess 

 nucleus, paranucleus ; contractile vacuole ; mouth, gullet, and anal spot ; 

 contractile fibres ; and sometimes bristles and stalks. Reproduction 

 effected by fission, gemmation, and spore-formation. Permanent or 

 temporary conjugation. Encystment. 



Holotricha: body uniformly covered with short cilia, no adoral 

 ciliated zone. Paramoecium aurelia, slipper animalcule ; Opalina 

 ranarum, without mouth and anus, parasitic in rectum of frog. 



Heterotricha : the entire body covered with cilia arranged in 

 longitudinal rows, an adoral band of cilia present. Stentor poly- 

 morphus (cceruleus) ; Balantidium and Nyctotherus in rectum of 

 frog. 



Hypotricha: mouth and anus placed on the ventral surface which 

 is provided with locomotor cilia and bristles, dorsal surface naked or 

 with fine tactile cilia. Stylonichia mytilus, Oxytricha gibba. 



Peritricha : cylindrical ; with an adoral spiral of cilia and fre- 

 quently with a girdle of cilia. Longitudinal fission. Vorticella 

 nebulifera, V. microstoma, Carchesium, Epistylis, bell animalcules, 

 all stalked. 



Order 3. Suctoria (Acinetaria, Tentaculifera). Usually fixed In- 

 fusorians, devoid of cilia in the adult condition, but possessing bundles 

 of suctorial tentacles. Reproduction chiefly by internal gemmation, with 

 production of free-swimming ciliated young. Acineta, Podophrya 

 gemmipara. 



