BEHAVIOR AND FUNCTIONS OF THE NUCLEUS 305 



fragments with too much nucleus had difficuhy in regenerating 

 and surviving and soon died, while Sokoloff (1924) found that 

 Bursaria fragments of the same sort did not regenerate. Weisz 

 (1948a), on the contrary, denied that excess nucleus was injurious. 

 The staunchest advocate of the importance of the nucleo- 

 cytoplasmic ratio in protozoa was Popoif (1909). But we have to 

 doubt, as an expression of over-exuberance for this idea, the report 

 that he produced dwarf lines of coeruleus from small fragments of 

 normal ratio, and note that his hopes for producing giant races of 

 stentors by the same principle were not fulfilled. In fact, Burnside 

 (1929) clearly demonstrated that Stentor fragments grow back to 

 the normal size before they divide, and this was fully confirmed 

 by Weisz (1948c). Yet PopoflF made a summary statement which 

 is probably valid : namely, that too much nucleus is not as injurious 

 as too little but is not without its eflFect. This remark is in part 

 substantiated in the following section. In the present connection, 

 my experience has been that hypernucleate fragments of coeruleus 

 often die prematurely or are notably tardy in regeneration (Tartar, 

 i959g) but this matter needs much more study (Fig. 86a). 

 Comandon and de Fonbrune (1939b) found that uninucleate 

 species of Amoeba carrying 3 nuclei by transplantation did not 

 divide though followed 2 months, but binucleates could divide. 



14. Consequences of reduced nucleus 



All but one macronuclear node can be removed from stentors 

 and the nucleo-cytoplasmic ratio can be still further shifted in 

 favor of the cytoplasm by grafting such an animal to one or more 

 completely enucleated stentors. A combination of excisions and 

 graftings therefore makes it possible in Stentor to produce truly 

 extraordinary shifts in the relative volumes of cytoplasm and 

 nucleus; and there is time to test the consequences because 

 compensatory growth of the nucleus occurs only later during 

 periods of oral primordium formation (Fig. 86c). 



These methods were not available to earlier workers whose cut 

 fragments yielded disturbance of the normal nucleo-plasmic ratio 

 in narrow^er range and gave no eflFect. Balbiani, for example, said 

 repeatedly (1889, 1891c, 1893) in reference to Stentor and other 

 ciliates that the relative size of the nucleus is indiflFerent for the 

 formative processes of regeneration. This was also the conclusion 



