6 4 



COLLEGE ZOOLOGY 



Stentor (Fig. 43, A) may be either fixed or free swimming. 

 It is trumpet-shaped when attached and pear-shaped when 

 swimming. The cuticle is striated and just beneath it are 



c.vac 



Tnunu 



mg.nu. 



a 



Fig. 43. — Infusoria. A, Stentor polymorphic of the order Heterotricha. 

 B, Stylonychia mytilus of the order Hypotricha. C, Vorticella of the order 

 Peritricha. D, Podophyra of the subclass Suctoria. c.vac, contractile 

 vacuole ; mg.nu, macronucleus ; mi.nu, micronucleus ; /, disc ; 2, mouth; 

 3, peristomial groove; 4, vibratile membrane in mouth; 5, ectoplasm; 6, endo- 

 plasm ; 7, food vacuoles ; 8, pharynx showing formation of food vacuoles ; 

 q, contractile vacuoles; 10, permanent receptacle into which contractile vacuole 

 opens; 11, micronucleus; 12, nucleus; 13, contractile fibrils running into 

 muscle in stalk; 14, stalk contracted (the axial fiber should touch the cuticle in 

 places). (A and B, from Weysse, after Kent; C, from Shipley and MacBride; 

 D, from Parker and Haswell.) 



muscle fibers (myonemes). The nucleus is ellipsoidal, or like 

 a row of beads. 



Order 3. Hypotricha (Fig. 43, B). — Ciliata with a flattened 

 body and dorsal and ventral surfaces. The dorsal surface is free 



