INGESTION IN THE CILIATE, FRONTONIA 341 



Since Closteriiim was the largest rigid body known to be ingested 

 by any frontonia, a study was made of the methods employed. 



In order to expediate observation, rich cultures of frontonia 

 were deprived of food for a number of hours (from twelve to 

 twenty-four), and were then removed to depression slides con- 

 taining numerous specimens of Closterium. Under these condi- 

 tions, the ciliates readily attacked the desmids until many fron- 

 tonias attempting ingestion could be observed at the same time. 

 In practically all cases ingestion was indeed only an attempt, 

 as complete ingestion was of very unusual occurrence as com- 

 pared with the number of trials. For example, on December 10, 

 1919, at 8:00 a.m., numerous specimens of Closterium were added 

 to a rich culture of hungry frontonias in a Syracuse watch- 

 glass, and the culture observed at brief intervals throughout 

 the day. Although the ciliates spent the day in almost con- 

 tinuous attempt at ingestion, only three could be found at 

 5:30 P.M. which contained closteria. 



The method of taking in these unusually large food particles 

 was found to be almost identical with that involved in the eat- 

 ing of oscillatoria filaments as recorded in the earlier part of this 

 paper, except that, of course, the mouth was more expanded. 

 The average limit of linear expansion is shown in figure 15. At 

 this point the organism either suddenly jerked back, whirled 

 about, and left the desmid, or allowed the mouth to recede 

 slowly down the desmid and completely ejected same, or re- 

 laxed as shown in A, figure 14, after which other attempts might 

 be made before the food was completely ejected. 



INGESTION OF SMALLER BLUE-GREEN ALGA FIBERS, OSCILLATORIA 



PROLIFICA, ETC. 



The five factors considered in the earlier part of this paper 

 are all noticeably effective during the ingestion of small flexible 

 fibers. Figures 17 to 21 show the fibers being formed into a 

 coil. The particular significance of this set of observations was 

 in the further demonstration that cyclosis, regardless of the 

 cause, is effective, if not essential, in some cases of ingestion. 

 Without assuming that this is actually the case, it would be 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 30, NO. 3 



