40 THE BIOLOGY OF STENTOR 



Johnson surmised that the pedal opening could be used for the 

 extrusion of pigment granules but in this he could have been mis- 

 led by appearances, as Weisz (1949a) noted, since the stickiness of 

 the detached holdfast is likely to pick up debris, including cast-off 

 pigment. However, Weisz stated that the discontinuity of the 

 ectoplasm at the foot can be used for the ejection of such waste 

 as the undigested pellicles of paramecia. 



3. Cytopyge 



Undigested material is usually collected and extruded at a single 

 site on the anterior left side, just below and to the left of the 

 opening of the contractile vacuole. As Johnson first described the 

 process, the spent food vacuoles, if small, accumulate by fusion 

 in this place. The pellicle then ruptures within one of the broad 

 granular bands and the waste is slowly defecated as the slit opens, 

 often so widely as to distort the adjacent striping; thereupon 

 closing without leaving a trace. 



Whether the cytopyge has a persisting structure is still in ques- 

 tion. Moxon (1869) could find no pore but said the spot was 

 marked by an irregularity in one or two of the granular stripes and 

 Johnson found no fixed organelle, but Andrews (1946) made out 

 a long slit with definite lips. Nevertheless, it is certain that defeca- 

 tion can occur in other places, as Johnson first observed. I twice 

 observed coeruleus ejecting solid material in the normal manner 

 simultaneously at two points far distant from the normal site 

 (Fig. 8a). Defecation openings break or open through granular 

 stripes, clear stripes carrying too much structure to permit exit. 



4. Contractile vacuole 



Stentors have but one contractile vacuole always located at the 

 left anterior side of the cell. The structure of this excretory system 

 seems to be less well-developed than in Paramecium in spite of the 

 fact that Stentors are much larger, e.g., there are no star shaped 

 canals and Haye (1930) found few lipoid granules associated with 

 this system. Walls of the contractile vacuole were not blackened in 

 osmic acid (Park, 1929). Schwalbe (1866) is said to have been the 

 first to see the excretory pore, in polymorphus. With its pigmenta- 

 tion, coeruleus shows this part more clearly and Moxon described 

 the presence of two or three unpigmented spots in the colored 



