AMCEBA AND SOME ALLIES: PROTOZOA 287 



Paramoecium is about .2 mm. (^ inch) in length. T<he 

 anterior end is rounded and the posterior end pointed. 

 Right and left sides are, as indicated in the figures, deter- 

 mined by the position of the mouth (Fig. 143, 2), which is 

 on a surface called ventral. 

 The entire surface of the 

 ectoplasm is covered with 

 great numbers of short, 

 hair-like structures, called 

 cilia (Fig. 143, l). The cilia 

 are the organs of locomo- 

 tion. Their customary 

 manner of working is to 

 wave backward toward the 

 posterior end, propelling 

 the animal forward, but 

 they may also wave so as 6-:-. 

 to send the body along 

 with the pointed end for- 

 ward. A few cilia j5pm- 

 what longer than the 

 Others lie in the groove FIG. 143. Paramoecium. Much enlarged 

 that leads diagonally across 

 the ventral surface to the 

 mouth. Their function *is 



B 



A, left side; B, ventral surface; 1, cilia; 

 2, mouth; 3, gullet; 4, food-vacuole 

 forming; 5, food-vacuole in cytoplasm; 

 6, anus; 7, contractile vacuole ; 8, mac- 

 ronucleus ; 9, micronucleus 



(From Sedgwick and Wilson's General 

 Biology) 



to carry the food down the 

 short gullet into the endo- 

 plasm. 



The endoplasm, which, as already explained, is that por- 

 tion of the cytoplasm lying between the nucleus and the out- 

 side layer of ectoplasm, is soft and semifluid. Food is passed 

 into it by the gullet (Fig. 143, 3), and immediately begins to 

 float away from that point, surrounded by a little drop of 

 water. These masses are called food-vacuoles (Fig. 143, 4, 5). 



