30 PROTOZOA 



Class 3. Infusoria. — In the Infusoria we find that the body is 

 provided with cilia useful in locomotion and the ingestion of food. 

 All Infusoria possess cilia in at least the immature condition, but in 

 a few forms they are replaced in the adult by tentacles. 



Subclass 1. Ciliata. — Infusoria having cilia throughout life. 

 They have a mouth, often with an undulating membrane. They 

 include five orders. 



Order i. Holotricha. — Primitive Infusoria with small uniform 

 cilia arranged in more or less spiral rows. (Examples: Paramecium^ 

 Colpoda.) 



Order 2. Heterotricha. — Infusoria in which small cilia are found 

 covering the body while the peristome is bordered with a spiral of 

 large adoral cilia. Fusion of the cilia into membranelles produces a 

 direct pathway to the mouth. (Example: Stentor.) 



Order j. Oligotrichida. — In this order the adoral zone forms a 

 ring around the margin of the peristome. Cilia are greatly reduced 

 or absent, and membranelles are the only motile organs. There are 

 three families, two of which are free living ( Halteridae and Tintin- 

 nidae), and the third consists of parasitic forms {Ophryoscolecidae) 

 in the stomach of ruminant mammals. (See page 482.) 



Order 4. Hypotricha. — Ciliata with a dorso-ventrally flattened 

 body. The dorsal surface has longitudinal rows of vestigial cilia 

 in the form of spines, while the ventral surface has hooks, fans, and 

 fringed plates. The hooked cirri act as legs. (Examples: Stylo- 

 nychia, Oxytricha.) 



Order 5. Peritricha. — Ciliata for the most part bare of cilia, 

 except in the oral region, and in some species with an aboral circlet 

 of cilia. The peristome bears a spiral band of large cilia, which 

 continues around the lid-like disc marking the distal end. Many of 

 the Peritricha are attached by a stalk which contains a contractile 

 fiber. (Examples: Vorticella, Epistylis.) 



Subclass 2. Suctoria {Jcinetaria, Teniae ulif era). — Infusoria 

 which have cilia in the young condition, but tubelike tentacles in 

 the adult. They have no locomotor organs except in the free- 

 swimming young, and are attached by a stalk. Other Infusoria are 

 caught by the tentacles and after the cuticle has been dissolved, the 

 fluid protoplasm is sucked down into the body of the suctorian. 

 (Examples: Podophyra; Dendrosoma, a colonial form.) 



Subclass 1. Ciliata. Infusoria. Order i. Holotricha. Type 

 — Paramecium caudatum. — Paramecium is a slipper-shaped, ciliated 



