PHYLUM PROTOZOA 



55 



Metabolism. The food of Paramecium consists principally 

 of BACTERIA and minute PROTOZOA. The cilia in the oral groove 

 (Fig. 33, o.g.) create a current of 

 water toward the mouth (m.). 

 Food particles are forced down the 

 gullet (g.) by a row of cilia which 

 have fused side by side, forming 

 an undulating membrane. At the 

 end of the gullet a food vacuole (f.v.) 

 is produced; this when fully formed 

 separates from the gullet and is 

 swept away by the rotary stream- 

 ing movement of the endoplasm, 

 known as cydosis. This carries 

 the food vacuole around a definite 

 course, as shown by the arrows in 

 Figure 33. Digestion occurs within 

 the food vacuole. Undigested par- 

 ticles are cast out at a definite 

 anal spot (Fig. 33, an.), which can 

 only be seen when the faces are 

 voided. The processes of diges- 

 tion, absorption, assimilation, ex- 

 cretion, and respiration are similar 

 to those described for Ameba. 



Behavior. LOCOMOTION. If 

 confined in close quarters, Para- 

 mecium exhibits elasticity, and can 

 squirm through small openings; 

 but when in a free field it swims 

 by means of its cilia. These are 

 inclined backward and obliquely, 

 so that the body is rotated in its 

 long axis over to the left as well 

 as propelled forward (Fig. 36). 



