336 WILLIAM M. GOLDSMITH 



contact with the food and exert a direct pull thereon and thus 

 actually pull the object into the mouth. Secondly, the action 

 of the cilia of the body may push the frontonia in the direction 

 of the food and thus force the end of the object through the mouth 

 opening. Prolonged study revealed the fact that both factors 

 of ingestion are employed. The most conclusive evidence in 

 support of the first possibility was found in the fact that the 

 organism was oftimes seen to lie quietly while the food slowly 

 entered the mouth ; while, on the other hand, it was not uncom- 

 mon for the oscillatoria fiber to remain comparatively still, 

 while the frontonia slowly moved forward as the end of the fiber 

 entered the mouth. This forward movement suggests that the 

 frontonia either pushes the fiber into its body by swimming toward 

 and around it or that the oral cilia, pulling upon one end of the 

 stationary fiber, move the frontonia in the direction of the food. 

 The fact that the ciliate at times moves forward when there is 

 a concavity at the oral region (fig. 4) suggests that the push comes 

 entirely from the locomotor organs. However, other situations 

 are noted wherein the oral region moves along the fiber while 

 the ciliate as a whole and the fiber itself are both stationary 

 (figs. 10 and 11, h to I). Such observations would seem to es- 

 tablish the fact that both the oral and locomotor cilia play a 

 part in the mechanics of ingestion. 



B. Body movement — third and fourth factors involved in the 

 mechanics of ingestion' 



In case the food particle is no longer than the expanded width 

 of the body of the ciliate, the two factors heretofore considered 

 suffice to explain ingestion. In the case of a diatom, for exam- 

 ple, the body cilia force the frontonia forward while the oral 

 cilia pull the food into the mouth. However, when one end of 

 the food body is forced against the aboral wall, as at a, figure 3, 

 and the other end still protrudes from the mouth, continued 

 ingestion, if no other factors entered, would cause a rigid fiber 

 to be thrust firmly against the aboral wall. Further ingestion 

 is impossible without the play of other factors, and these appear 

 to result from the stimulation due to the pressure of the end of 



