200 



THE BIOLOGY OF STENTOR 



Fig. 55, Observations concerning polarity. 



A. Heteromorphic specimen from abortive fission of a 

 divider grafted to a regenerator, showing tendency toward 



resorption of conflicting part. 



B. Heteromorph with continuous striping and therefore 

 reversed asymmetry in the smaller part, consequence of hetero- 

 polar implant (later separating) which set up a secondary polar 



axis. 



C. When major portion of stentor is reversed (head and tail 

 trade places) all parts retain their polarities and mid-portion 



regenerates separate head (x) and tail (3;). 



D. Head excised and grafted to replace tail at posterior end 

 does not reverse the cell polarity nor prevent regeneration of the 



"host" but organizes a new individuality. 



the center of organization and growth of a secondary cell shape 

 (Fig. 55D). From the standpoint of oral inhibition these cases were 

 also interesting as showing that a displaced set of intact feeding 

 organelles can much delay primordiiim formation but not prevent 

 it entirely. 



All these experiments so attest the fixity of polarity in every 

 part of the cortex that one wonders whether reversal of polarity is 

 ever possible. It would seem that the best place to look for such a 



