Protozoa. 167 



is the oral groove. Observe the cilia along the margins of the 

 disk and the peristome. The extension of this groove into the 

 body forms the gullet. Vorticella has a long, curved macro- 

 nucleus and a small, spherical micronucleus, but these are not 

 easily seen. Add a little dilute acetic acid. 



2. Movements. Observe carefully the stalk during and after 

 the coiling. The stalk does not contain any of the endqsarc, 

 but only the ectosarc and cuticle. Note also the changes in the 

 shape of the body and the rearrangement of the parts. In what 

 order are the parts folded in during the act of closing, and in 

 what order are they expanded when the vorticella extends 

 again ? Tap on the slide while watching to see these changes. 

 Make sketches showing the fully expanded and the closed forms. 

 Why does the vorticella thus draw itself close to its support ? 



3. Feeding and Digestion. Watch the vibrations of the cilia. 

 Can you see that food particles are swept into the oral groove 

 and down to the blind end of the gullet ? Add powdered car- 

 mine or indigo to the water. Can you see food balls at various 

 points in the endosarc ? Are they stationary, or do they move ? 

 If they move, do they go in any regular order ? Look closely for 

 the expulsion of residue into one side of the gullet, and so out 

 by the return current. Does a vorticella move toward food ? 

 Could it do so ? Does it need to do so ? Does vorticella show 

 choice in the particles that it takes as food ? 



4. Excretion. Find the pulsating vacuole. Time its con- 

 tractions. 



5 . Senses. What senses does the vorticella appear to possess ? 



6. Reproduction. Look for two vorticellae on one stem. You 

 may find one in the early stages of division. When one of these 

 becomes separated, learn how it swims away. Study vorticellae 

 a long time to find out about the mode of development, making 

 sketches of what you observe. 



Topics for Reports. Chalk. Barbadoes Earth. Malaria. 

 Infusorial Earth. 



