io8 



THE BIOLOGY OF STENTOR 



healing is an important factor in regeneration (Causin, 1931; 

 Weisz, 1948a). Weisz's (1951b) statement that any portion of the 

 endoplasm is capable of supporting regeneration is subsumed in 

 the fact that no significant amount of endoplasm is needed at all. 



Fig. 25. Regeneration of coeruleus under severe conditions. 



A. Mid-ring fragments regenerate in spite of extensive wound 

 surface and exposure of endoplasm, because the piece folds to 

 cover surface with ectoplasm and anlage promptly appears in 

 short section of original primordium site. A normal stentor can 



be formed within a day. 



B. Specimens with collapsed ectoplasm after removal of 

 practically all the endoplasm by vigorous pipetting can regenerate 



and fill out the cell shape within a day. 



C. In nucleated endoplasmic spheres with almost all the 

 cortical layer excised the remaining ectoplasm stretches to cover, 

 with granular bands becoming excessively broad and pale. 

 Here the reconstitution was abnormal and the primordium, 

 appearing on the "wrong" side, produced a stentor of reversed 

 asymmetry. Usually such specimens, with greatly reduced 

 ectoplasm do not live or regenerate, possibly because even 

 maximum stretching cannot achieve a cortical continuum with 



no "edges". (After Tartar, 1956c.) 



