AMEBOID MOVEMENT 99 



b 



Figure 32. Showing ingestion of alga filaments in Frontonia leucas. a, 

 the beginning of the ingestion of an alga filament. Note the streaming of 

 the endoplasm preceding the end of the filament, b, almost two complete 

 coils of the filament have been rolled up inside the Frontonia by the rotary 

 streaming endoplasm. The endoplasm in the center of the animal is 

 stationary, c, a filament, if thin, may be grasped anywhere along its 

 length, bent together and swallowed in the usual manner. Diameter of a, 

 250 microns. 



tonia and paramecium rapid endoplasmic streaming precedes for 

 a short distance the forward end of the ingested filament or the 

 food vacuole (Figure 32, a). 



If a filament of alga is too long for the Frontonia, or one end 

 of it is fast, streaming is reversed after several coils have been 

 rolled up and the filament is ejected. So far as could be observed, 

 the streaming process is reversed in all details, though the rate of 

 ejection seemed to be somewhat slower than the rate of ingestion. 

 Occasionally, however, ejection is accomplished much more 

 quickly. If there are several coils of a filament whose other end 

 is fast, rolled up inside of a Frontonia, the mouth sometimes 

 stretches antero-posteriorly until the coil as a whole without un- 

 winding is thrown out of the body. The viscosity of the endo- 

 plasm might lead one to expect that some of the endoplasm would 

 foe brought out with the alga, but such is not the case. 



The essential differences between rotational streaming in Fron- 

 tonia and in paramecium are: (i) It is under the control of the 

 organism in Frontonia while in paramecium it is a continuous re- 

 versible process. (2) It is much more rapid in Frontonia than in 

 paramecium. On the other hand, the physics of streaming in 



