334 WILLIAM M. GOLDSMITH 



5. Food is not taken into the mouth by the usual ciUary action 

 of the cytostome. A number of related factors are involved 

 in this process. These are considered in the text and are listed 

 in the summary. 



GENERAL BEHAVIOR 



Under normal conditions, in a quiet culture, frontonias may 

 be seen swimming slowly here and there near the substratum 

 apparently in quest of food. Any slight disturbance, such as 

 the jarring of the container or the addition of weak chemicals 

 to the culture, causes the organisms to rise from the bottom and 

 to swim around more rapidly. However, after the removal of 

 the stimulus they soon settle down to the bottom and continue 

 the slowly swinaming movements. Schaeffer ('' Ameboid Move- 

 ment," '20) says: 'Trontonia feeds mostly by 'browsing,' that 

 is by eating particles lying on or against some solid support." 

 If an individual chances to come in contact with any object 

 approximating the size of the food it is accustomed to eating, 

 such as filaments of oscillatorias, diatoms, desmids, and various 

 other microscopic plants, it usually pauses, places the oral 

 opening near the object and proceeds to brush it with the oral 

 cilia as though attempting to ascertain its nature (fig. 1). While 

 the mouth is in close proximity with the object, the posterior 

 part of the body frequently swings about this point as upon 

 a pivot, sometimes turning through an arc of 90° or even entirely 

 around. It is not uncommon for the organism to leave the 

 object, move off for a short distance, then turn slowly about 

 and swim here and there over the same area, eventually coming 

 in contact with the same object and repeating the process. 



THE MECHANICS OF INGESTION 



Although frontonias ingest food particles of various shapes, 

 the process of feeding can be more successfully observed when 

 the food is in the shape of a filament. Before actual ingestion 

 is begun the organism usually moves over the food and slowly 

 swings around until the longitudinal axis is parallel with the 

 long axis of the object to be engulfed. It then moves slowly 



