INGESTION IN THE CILIATE, FRONTONIA 335 



forward with the oral ciha in contact with the object (fig. 1) 

 until the end of the linear food particle is reached, when the 

 mouth is slowly pushed over the end of the object and thus 

 ingestion begins (fig. 2). 



Just as the oscillatoria filament is about to enter the mouth, 

 the frontonia bends the anterior end downward as shown in 

 figure 2. This brings the plane of the mouth perpendicular to 

 the long axis of the fiber, and thus permits the fiber to enter with 

 the least resistance. As the fiber slowly enters the body, the 

 granules and food particles suspended in the endoplasm are 

 pushed aside, leaving a clear space on either side of the entering 

 food. This space usually presents the general appearance of 

 the ectoplasm. From all indications it seems quite certain 

 that a small amount of water is taken in with the fiber which 

 adds to the transparency of the surrounding space. This clear 

 area is not definitely set off from the endoplasm material as is 

 the case during the last two or three hours of digestion. The 

 protoplasmic granules and smaller food particles may pass from 

 one area to the other, and often crowd in and at times, and at 

 certain places, obliterate the transparent space. The movement 

 of these granules in front of and to the side of (fig. 3) the incom- 

 ing food fiber is quite characteristic of the movements accom- 

 panying the entrance of any solid into a viscous medium con- 

 taining particles in suspension. As will be suggested later, 

 there is little streaming of the granular endoplasm unless there 

 is first a movement of the incoming fiber or possibly a contrac- 

 tion or other movement of the body wall. 



A. Ciliary action — first and second factors of ingestion 



The mechanics by which the oscillatoria filament (or any other 

 material) is caused to enter the body of the frontonia is of 

 vital interest in connection with the present investigations. At 

 the outset it should be emphasized that the customary method 

 employed by the ciliates, namely, the sweeping of food particles 

 into the mouth in a current of water created by the cilia, is 

 obviously out of the question, since the food is oftentimes much 

 longer than the organism. First, the oral cilia may be in actual 



