REORGANIZATION 



97 



oral region only. It should also be mentioned that although injury 

 to the cell usually causes resorption of early primordia in dividers, 

 this occurs very rarely in reorganizers. In every case w^hen early, 

 stage-2 reorganizers w^ere split into a clover-leaf shape the primor- 

 dium was not resorbed and the animals completed reorganization 

 after the parts of the cell fused together. Such persistence of the 

 anlage almost always did not occur in dividers unless the mouth- 

 parts were also excised at the time the cell was split. Therefore the 

 reorganizers behaved as if their mouthparts were not present, i.e., 

 as if these parts were effectively, if cryptically, isolated somehow 

 from the rest of the cell. This hypothetical, morphological dis- 

 junction of parts would be of a subtle nature, however — possibly 

 at the level of fine fiber structures — for when I tried to duplicate 

 it by sectioning the membranellar band with a needle at the point 

 where it meets the oral pouch, the band merely mended together 

 and there was no reorganization. Obvious isolation of mouthparts 



Fig. 23. "Autotomy" of mouthparts. 

 a: Head of stentor rotated 180° with mouth now opposite the 

 primordium site, h: Several days later the mouthparts — such 

 as are resorbed in reorganization :^— separate from the mem- 

 branellar band and move into the frontal field, with ends of the 

 band rejoining behind them. Then a "reorganization" primor- 

 dium appears, c: Old mouthparts cut into the frontal field are 

 then resorbed, together with part of the membranellar band 

 which permits integration of the anlage to produce a stentor of 

 normal orientation. 



