REORGANIZATION IO3 



had previously observed. This earlier investigator also noted that 

 without primordium formation and nuclear clumping there are at 

 most only one or two nodes which may divide. Schwartz com- 

 pletely cinched the point by showing that regeneration of the 

 depleted macronucleus occurs only after primordium formation, 

 when there is also a mitotic division of the micronuclei leading to 

 their increase in number. Moreover, such an increase in the nuclear 

 complement seemed definitely to be called for, because he found 

 that the "entire metabolism" of stentors with reduced nucleus is 

 upset. After great reduction of the macronuclear volume there 

 may follow a series of reorganizations, according to Schwartz, with 

 the implication that in each only a limited increase in the macro- 

 nucleus is possible. This I have also observed. 



That mitotic multiplication of the micronuclei occurs during 

 reorganization when there is the increase in the number of macro- 

 nuclear nodes, Schwartz deduced as follows. If one assumes that 

 in division there is but a single mitosis of each micronucleus so 

 that the total number is only doubled, then the demonstrated 

 presence of about the usual number of these nuclei in both 

 daughter cells of a stentor which had previously been induced to 

 reorganize by removing most of the macronucleus (and therefore 

 most of the adhering micronuclei) implies that the micronuclei as 

 well as the macronuclear nodes must have increased during the 

 reorganization. Furthermore, it has been demonstrated directly 

 in Blepharisma that micronuclear mitosis accompanies reorganiza- 

 tion (Suzuki, 1957). 



It may well be that anything which may lead to a macronucleus 

 becoming too small for the cell volume results in reorganization. 

 The essence of reorganization would then not lie in the fact that 

 the mouthparts are replaced, for this also occurs after excision of 

 substantial lengths of the membranellar band. Nor would it be a 

 response to injured or worn-out mouthparts, since this is essentially 

 regeneration and the evidence for this condition's being the neces- 

 sary cause of reorganization is overwhelmingly in the negative. 

 Changing the medium does not in my experience act as a stimulus 

 to epidemics of reorganization, and reorganizers are found in 

 cultures that have not been altered. Hence it would seem proper to 

 regard reorganization as a wholly spontaneous and intrinsic 

 response to certain disproportionalities or disarrangements of parts 



