26o THE BIOLOGY OF STENTOR 



isolated into a large drop of coarse-filtered medium on a depression 

 slide. The reality of hunger divisions in stentors therefore remains 

 still in question. 



Many have observed that in the largest stentors, coeruleiis and 

 polymorphus, dwarf forms appear under conditions of starvation 

 (Maupas, 1888; Johnson, 1893; Popoflr, 1909; Prowazek, 1904 

 and Schulze, 1951). Stolte (1922) observed both large and small 

 forms in starving cultures. I have myself frequently noted a similar 

 range in size which is not always correlated with cannibalism. 

 Possibly the larger forms are animals which had recently divided, 

 do not then divide further after food is withheld, and therefore 

 would gradually diminish only through the utilization of their own 

 substance. To complete this historical resume Sosnowsky (1899), 

 as reported by Sokoloff (1923), stated that division in stentor is 

 stimulated by starvation, and that the macronuclear membrane 

 disappears under these conditions. Ivanic (1927) contributed the 

 equally improbable notion that, when feeding is stopped, stentors 

 and other protozoa actually increase in size as they use up the 

 remaining food but fail to divide. 



Several visible changes besides decrease in cell volume occur 

 during starvation. In coeruleus and perhaps in other pigmented 

 stentors the coloration tends to disappear. This fading to nearly 

 white is conspicuous in single animals long isolated on slides, but 

 larger samples in a culture dish remain fairly green for a month or 

 more though starved. Weisz (1949a) thought that the pigment 

 granules are digested during starvation. Granular bands do seem 

 eventually to disappear in isolated animals, but only as death 

 approaches. But stentorin itself is certainly not easily assimilated 

 in cannibals and the pigment may even be ejected as waste. 

 Pigment changes are therefore enigmatic and require much more 

 study. Stolte (1922) emphasized that starvation produces vacuoli- 

 zation of the endoplasm but this pathological state, again, is 

 prominent only near the point of death. An important alteration 

 which occurs only gradually is that the macronucleus becomes 

 reduced. On the evidence it cannot be decided whether this is 

 because the substance of the nucleus is drawn upon to maintain 

 life or because the nucleus is adapting in size to the decreasing 

 volume of cytoplasm, or both. That regulation of nuclear to 

 cytoplasmic volume is more important than consuming the nucleus 



