86 



THE BIOLOGY OF STENTOR 



primordium this site is by no means the necessary initiator of 

 furrow formation. The same is also indicated by a case in which 

 the primordium of a stage-3 divider was shifted to the posterior 

 end; the cell still divided in two (Fig. 19B). Nevertheless if for 

 any reason the dividing stentor resorbs the oral primordium itself, 

 division is then not continued (Weisz, 1956; Tartar, 1958c). 



A 



B 



Fig. 19. Persistence of division in spite of major disturbances; 

 separation of a heteropolar pair. 



