THE BELL-AiSIMALCULE. 61 



1. The projecting outer rim is the peristome. 



2. The central disk, projecting above the peristome. 



3. The short, hair-like cilia on the border of the disk 

 and peristome ; watch the motion of these cilia, and 

 the currents of water thus produced. 



4. A depression between the peristome and disk, deep- 

 ening at one place to make the vestibule, or entrance 

 to the gullet, which extends a short way into the 

 body. 



5. A clear space, just under the disk, is the contractile 

 vesicle; watch this closely for some time; what 

 changes occur? 



6. At various points in the body may be seen rounded 

 masses, the food-balls; do they remain of the same 

 size, and keep the same place ? 



7. Make drawings showing the above points. 



Watch patiently to see the accumulation of particles at 

 the lower end of the gullet; after a time this mass may 

 be seen to be pushed into the body. This forms one of 

 the food-balls. These food-balls may be seen moving on 

 in a circle within the body. Ejection of undigested mat- 

 ter takes place near the mouth. Sometimes two vorti- 

 cella are found on one stalk ; by watching it patiently it 

 may be found that the vorticella is dividing to form two 

 vorticellse ; this is one way these animals have of repro- 

 ducing. What powers and faculties have you and the 

 vorticella in common ? 



Read " The Structure of Vorticella " in Brooks' " Hand- 

 book of Invertebrate Zoology." 



