274 THE BIOLOGY OF STENTOR 



vacuoles. Filtered Astasia culture fluid also killed the stentors when 

 transferred into it. 



Somewhat resembling Schonfeld's account, a student (William 

 I^ewis, 1959) has recently observed that coeruleus may ingest and 

 form food vacuoles of the flagellate Rhabdomonas incurva but the 

 prey passes through the stentors, emerging by defecation in a 

 living and active state. This could be the beginning of parasitism, 

 since at least many of the flagellates enter the stentor but are 

 protected against digestion. 



We may choose this place to mention a report that stentors are 

 possibly toxic to other organisms. Otterstrom and Larsen (1946) 

 very doubtfully attributed kills of fingerling fish in hatchery ponds 

 to wild (but not to cultured) Stentor polymorphus producing toxins 

 only when irritated. 



7. Abnormal stentors 



Here we shall describe certain abnormalities in coeruleus relating 

 to the pigment granules which sometimes arise without operational 

 interference in cultures or stentor samples. Whether these aberrant 

 forms are due primarily to disturbance of metabolism or involve 

 other factors and even racial differences as well we do not know. 

 Very little is yet known about the abnormal animals themselves 

 or their origin, but they offer promising Unes for further study. 



(a) Depigmented stentors 



In starving samples of coeruleus and even rarely in normal 

 cultures one finds stentors which are nearly devoid of pigment 

 granules and appear colorless. Stolte (1922) thought that the 

 amount of pigmentation is a function of metabolism and decreases 

 with decreasing oxygen tension, but the presence of both green 

 and white forms in the same culture or sample implies that external 

 conditions are not wholly determinative. Colorless coeruleus were 

 seen by Schuberg (1890), Johnson (1893), and Gelei (1927). 

 Johnson concluded that the pigment granules had been excreted 

 or ejected, because green clots were found in the sample dish or 

 attached near the base of the stentors. In my observation white 

 coeruleus retain a very few pigment granules in bands which then 

 appear not granular but trabecular, indicating that the granular 

 bands do have some intrinsic structure. Hetherington (1932b) 



