THE PROTOZOA 



219 



m~ 



(Fig . 1 3 2 , tr) , and are prob- 

 ably weapons of offense 

 and defense. When a lit- 

 tle acetic acid is added 

 to the water, they ex- 

 plode, discharging long 

 threads. 



Food. — The food of 

 Paramecium consists prin- 

 cipally of minute plants 

 and animals. The cilia 

 in the oral groove (Fig. 

 132, o.g) create a current 

 of water which forces the 

 food particles down the 

 gullet (g). At the end 

 of the gullet a food vac- 

 uole (/.!)) is produced; 

 this when fully formed 

 separates from the gullet 

 and is swept away by the 

 rotary streaming move- 

 ments of the fluid within 

 the body. This carries 

 the food vacuole around a 

 definite course, as shown 

 by the arrows in Figure 

 132. 



Physiological Pro- 

 cesses. — Digestion takes 

 place without the aid of 

 a stomach. After a food vacuole has become embedded 

 in the body an acid secretion enters through its walls and dis- 

 solves part of the food. Undigested particles, the feces, are 

 ejected at a definite anal spot (Fig. 132, an). 



-Fig. 132. — Paramecium viewed from the oral 



surface. 



L, left side ; R, right side. 



an, anus ; ec. ectosarc ; en, endosarc ; f .v, 

 food vacuoles ; g, gullet ; m, mouth, ma, ma- 

 cronucleus ; mi, micronucleus ; o.g, oral 

 groove ; p, pellicle ; tr, trichocyst layer. The 

 arrows show the direction of movement of the 

 food vacuoles. (From Jennings.) 



