PHYLUM PROTOZOA 65 



from cilia, but spines may be present. The ventral surface is 

 provided with longitudinal rows of cilia and also spines and 

 hooked cirri, which are used as locomotor organs in creeping 

 about. The cilia around the oral groove aid in swimming as 

 well as in food taking. There is a macronucleus, often divided, 

 and two or four micronuclei. Examples: Oxytricha, Stylo- 

 nychia. A side view of a creeping Stylonychia is shown in 

 Figure 43, B. 



Order 4. Peritricha (Fig. 43, C). — Ciliata with an adoral 

 ciliated spiral, the rest of the body is without cilia, except in a 

 few species where a circlet of cilia occurs near the aboral end. 

 Examples: Vo'rticella (Fig. 43, C), Carchesium, Zoothamniutn. 



The common members of this order are bell-shaped and at- 

 tached by a contractile stalk. Certain species are solitary 

 (Vorticella, Fig. 43, C), others form tree-like colonies (Car- 

 chesium), and still others are colonial but with an enveloping 

 mass of jelly (Zoothamniutn). The anatomy of Vorticella is 

 shown in Figure 43, C. The stalk contains a winding fiber com- 

 posed of myoneme fibrils; this fiber, on contracting, draws the 

 stalk into a shape like a coil spring. 



Subclass 2. Suctoria. — Infusoria without cilia in the 

 adult stage. No locomotor organs are present and the animals 

 are attached either directly or by a stalk. No oral groove nor 

 mouth occurs, but a number of tubelike tentacles extend out 

 through the cuticle. Examples: Podophyra (Fig. 43, D), 

 Sphcerophyra. 



Ciliates are captured by these tentacles and their substance is 

 sucked by them into the body. Both fresh- water and marine 

 species are known. Podophyra (Fig. 43, D) is a well-known 

 fresh- water form. Sphcerophyra is parasitic in other Infusoria. 



5. Protozoa in General 



Protozoa may be defined as unicellular animals which in 

 many cases form colonies. An examination of the types dis- 

 cussed in the preceding pages will show that the Protozoa differ 



