INTRODUCTION 3 



the transfer from one cell to another of nuclei retained within a 

 thin envelope of endoplasm, allowing enucleated cells to be 

 renucleated at any time or the nucleus of one species to be sub- 

 stituted for that of another with practically no admixture of 

 cytoplasms. 



When added to the simpler experiments on stentor fragments 

 in which parts become wholes, the possibilities afforded by these 

 operations and their permutations appear endless. The organic 

 integration by which new individualities become one can be 

 explored. Nucleo-cytoplasmic interactions and the nature of 

 species differences are opened to inquiry with fresh material. 

 Problems of polarity can be explored in heteropolar grafts of cells 

 and cell parts. Cell differentiation under a variety of conditions 

 occurs before our eyes. The intimate nature of aging, necrosis, 

 and damage by various external agents can be investigated by 

 testing the revival of " sick " animals after grafting them to healthy 

 cells or cell parts in stentors as in the important work which 

 Daniels (1958) is doing with giant amoebas. These are only a 

 sampling of what can be done. 



Stentors share, now or potentially, experimental advantages 

 common to many protozoa. As free-living cells they are directly 

 affected by alterations in the fluid medium ; and it has been found 

 that certain substances added to the medium may produce profound 

 effects in the behaviour, reproduction, and morphogenesis of 

 stentors. Since stentors undergo sexual conjugation at times, 

 genetic experiments should eventually be possible. Irradiation or 

 other treatments at the time when the nuclear complement is 

 reduced to a simple anlage could produce mutations as genetic 

 markers and indicators of cell activities. If mating types appear 

 as in other ciliates we would have a differentiating characterization 

 in the expression of which the roles of nucleus and cytoplasm 

 could be investigated by direct operations. A fundamental need 

 in the cancer problem as well as of general biological under- 

 standing is to learn precisely what incites the cell to division, 

 whether it be an egg, a tissue cell, or a protozoan. The great 

 amenability of stentors to manipulation encourages us to search 

 for the answer in them. 



Each of these experimental possibilities is important in itself 

 but their unique combination within one organism makes Stentor 



