4 PROTOZOA. 



CLASS 4. Infusoria. 



With motile organs in the form of cilia during 

 all or part of the life cycle. Nucleus dimorphic 

 (macronucleus and micronucleus). Reproduc- 

 tion is by simple transverse division or by bud- 

 ding. 

 Subclass 1. Ciliata. 



With cilia throughout the life-history 



Order 1. Holotrichida. 



The cilia are of approximately equal length and 

 equally distributed over the body. Tricho- 

 cysts are frequently present. (Prorodon, Didi- 

 nium, Paramecium.) 



Order 2. Heterotrichida. 



With a uniform covering of cilia, together with 

 an "adoral zone" formed of cilia fused into 

 membranelles. (Spirostomum, Stentor, Halte- 

 ria.) 



Order 3. Hypotrichida. 



The cilia are limited to the ventral surface of a 

 dorso-ventrally flattened body. Cilia often 

 fused into cirri, membranelles, etc. (Oxy- 

 tricha, Pleurotricha, Euplotes, Stylonychia.) 



Order 4, Peritrichida. 



More or less bell-shaped in form. Cilia usually 

 reduced to those constituting the adoral zone. 

 (Vorticella, Zoothamnium, Lichnophora.) 

 Subclass 2. Acinetaria. 



Usually possessing cilia only during the embry- 

 onic stages of the life-history. Tentacles 

 adapted for piercing and sucking are present. 

 (Podophrya, Ephelota, Acineta.) 



Blochmann: Die Mikroscopische Tierwelt des Siisswassers. Abt. 1. Pro- 

 tozoa, 1895. 



Biitschli: Protozoa. Bronn's Thierreich, 1889. 



Calkins: Protozoa, 1901. 



: Protozoology, 1909. 



: Marine Protozoa of Woods Hole. Bui. U. S. Fish. Com., 1901. 



Conn: Fresh Water Protozoa of Connecticut. Bui. State Nat. Hist. 

 Surv., 1905. 



Doflein: Lehrbuch der Protozoenkunde. 4 Auf., 1916. 



Edmondson: Protozoa of Iowa. Davenport Acad. Sci., 1906. 



Hartrnann: Praktikum der Protozoologie, 1910. 



Jennings: Behavior of the Lower Organisms, 1906. 



: Life and Death, Heredity, and Evolution in Unicellular Organisms, 



1920. 



