BEHAVIOR AND FUNCTIONS OF THE NUCLEUS 303 



normal starving animals (Tartar, 1956c). This corresponds to 

 Brachet's (1955) results with Amoeba * 



Allied to the problem of digestion is the matter of autolysis or 

 '' self -digestion " or the capacity of enucleated ciliates to dedifferen- 

 tiate and resorb existing ectoplasmic structures. As is too often 

 disturbingly the case, some say they do and others say they don't. 

 In Frofttonia, Balbiani (1889) observed the disappearance of tri- 

 chocysts and much of the ciliation in enucleates and he thought 

 this might be an autodigestion of proteins. Schmahl (1926) said that 

 membranelles are resorbed in enucleated Bursaria; but he 

 remarked that Dembowska found no resorption of parts in 

 Stylonychia after enucleation. Specifically in regard to Stentor 

 coeruleus, we have already noted that early primordia are resorbed 

 when the nucleus is removed, but the situation is quite different 

 in respect to already formed structures. 



Weisz (1949c) claimed that enucleation produces prompt 

 dedifferentiation of existing feeding organelles and holdfast within 

 24 hours. He therefore believed that the nucleus is necessary not 

 only for the production of new parts but equally for the main- 

 tenance of structures already formed. My experience has been to 

 the contrary (Tartar, 1953). I obtained no impression that the 

 feeding organelles soon disappear upon withdrawal of nuclear 

 ''support". Most frequently animals died with these organelles 

 intact or, at most, a bit vague. Only when survival of enucleates 

 was most protracted did extensive dedifferentiation finally occur 

 (Fig. 85B), but since dedifferentiation was then so tardy it was 

 probably the result rather of general necrosis. In the present 

 context it is significant that in the experiments in which the heads, 

 only, of stentors were excised, proportionality of parts, which 

 undoubtedly involved resorption of considerable part of the 



*Regarding transport mechanisms in the cell, de Terra (i960) found 

 in S. coeruleus that during the later stages of division, after the macro- 

 nucleus has condensed, uptake of phosphate as tested by radio-active 

 phosphorus 32 is greatly reduced. This reduction occurred both in 

 nucleate and enucleated animals. Return to high uptake after division was 

 found only in cells with the macronucleus. Hence by inference this nucleus 

 is chemically inactive during late fission (which therefore does not require 

 the nucleus for completion), or at least the macronucleus is required for 

 restoration of high phosphate uptake characteristic of the interdivisional 

 period. 



