280 University of California Public-ations in, Zoology [Vol.20 



Feeding is the chief function of the acloral cilia. Thej^ are closely 

 coordinated in action, as is shown by the fact that in degenerating in- 

 dividuals they will beat in unison after other cilia beat only erratically 

 or have ceased entirely. Coordination is most pronounced in the cilia 

 of the left lip. The action of the adoral cilia produces a strong eddy 

 in the surrounding medium with the vortex of the eddy within the 

 peristome. In the above description it was noted that the right lip 

 projected slightly forming a ledge or bank. The current produced 

 by the cilia strikes against this ledge and solid objects are deflected 

 into the underlying cytostome. The natural rotation of the animal 

 on its longitudinal axis as described above aids in this process, for the 

 right lip thus acts as the blade of an auger. The food particles pass 

 down the oesophagus and collect at the inner end in a sort of droplet. 

 After several bits have been collected, the droplet begins its circulation 

 in the endoplasm as a food vacuole. 



The closure of the cytostome in all probability is effected by the 

 oral plug. The latter is very mobile and contains fibers of the neuro- 

 motor apparatus. It has frequently been seen to project anteriorly 

 in a knoblike protrusion (pi. 28, fig. 14). This same phenomenon was 

 observed by Wising (1871). In view of its situation, its sensitivity, 

 and its mobility, it seems plausible to interpret it as an oral plug 

 with essentially the same function as the oral disk of Diplodinium 

 ecauclatum (Sharp, 1914). 



The discharge of indigestible portions of the food takes place at 

 a constant point at the posterior end of the animal, the cytopyge {cyt., 

 fig. I). It is an opening, however, only at the time of discharge. 

 At other times there is only a thinning of the cortical layer which can 

 be identified with comparative ease in fixed material. In the living 

 organism the process of defecation was frequently observed. The 

 undigested particles become segregated at the extreme posterior end 

 in a sort of vacuole, the rectal vacuole {ret. v., fig. I; pi. 28, fig. 13). 

 After this vacuole has become of considerable size (often filling one- 

 third of the cell in degenerating forms) the pellicle over the cytopyge 

 ruptures and the contents are discharged. The pellicle quickly forms 

 again closing the aperture, collection of indigestible particles in the 

 rectal vacuole continues, and the process is repeated. 



The cantractile vacuoles (post. c. v., ant.c.v., fig. I) are two in 

 number, usually situated on the dorsal side, one anteriorly, well up 

 toward the apical cone, the other in the posterior one-third of the 

 organism. There is a great deal of variation in their location in 

 different animals, though in the individual their situation seems to be 



