PROTOZOA. 



161 



rim of the bell is drawn ejuickly together, the bell 

 becomes almost spherical, and by this action the food 

 is forced downward into the mouth. There is no 

 stomach or hollow body cavity. The food is merely 

 crowded into the body mass, as a stone can he crowded 

 into a lump of dough. 



Microscopic Objects. 



VORTICELLA. 



CAKCHESIUM. 



Vorticella proper has only one bell on one stalk. 

 The stalk does not branch. 



In Carchesium, the stalk branches and each 

 branch bears a bell at its extremity, the whole colony 

 looking like a tree with a flower bell at the tip of 

 each twig. The bell and the stalk are both con- 

 tractile. 



In Epistylis, the stalk branches as in Carchesium. 

 The bell, however, is somewhat more elongated, and 

 the stalk is not contractile. 



Usually, in the body of the bell, several food 

 masses may be found which are readily distinguish- 

 able by their color, and a clear, transparent body may 

 be seen which, at intervals of half a minute or more, 

 gradually contracts and disappears and soon reap- 

 pears. This is called the contractile vesicle. 



