INGESTION IN THE CILIATE, FRONTONIA 339 



gestion were, of course, futile, but the process was nevertheless 

 normal. This repetition made it possible to observe in detail 

 again and again all of the movements involved in the ingestion 

 of the same fiber by the same frontonia. These observations 

 were furthermore especially valuable, as the fiber bent at a 

 weak place at a distance from the ingested end equal to the ex- 

 panded length of the ciliate. This bending permitted each 

 process to continue more than twice as long as it otherwise 

 would have done, since it was possible for more of the fiber to 

 be ingested. 



C. Cyclosis, the fifth factor of ingestion 



Schaeffer emphasizes the fact that ''in Frontonia leucas, ro- 

 tational streaming is under the control of the organism, and 

 special use is made of it in feeding." Although it wall be shown 

 later that cyclosis is effective, and in some cases essential, dur- 

 ing the ingestion of certain flexible fibers, observations show that 

 with some food material complete ingestion takes place without 

 this fifth factor. A reconsideration of figures 1 to 9 will illustrate 

 the point under consideration. In this case the rigid alga fila- 

 ment is forced into the body by the pull of the oral cilia and the 

 push of the locomotor cilia of the body wall. The rotation of 

 the body relieves the tension point (fig. 3, a) and permits the 

 end of the fiber to pass down the aboral wall. Although there 

 are slight indications of cyclosis during the ingestion of material 

 of this type, careful observation makes it evident that rotational 

 streaming is not essential. It might be concluded, then, that 

 rigid material whose length is no greater than the expanded 

 length of the frontonia can be, and is, ingested without the effec- 

 tive play of cyclosis. 



VARIATION IN SIZE OF MOUTH 



Such observations on ejection of partly ingested material as 

 those considered above revealed some interesting facts regarding 

 the nature of the mouth of frontonia. In many cases specimens 

 which had ingested a sufficiently long fiber to produce a coil 

 inside of the body suddenly whirled about and caused the mouth 



