REORGANIZATION 99 



logical regeneration. In either case there should be less successful 

 feeding and one would expect that reorganizers would appear 

 under-fed, transparent, and with few if any food vacuoles. But as 

 I recently pointed out (Tartar, 1958c) reorganizers are quite as 

 replete as their fellows. In fact, Weisz (1949a, 1954) almost 

 implied this himself in explaining that pigment granules and 

 carbohydrate reserves are not decreased and utilized in re- 

 organization as they are in regeneration because reorganizers can 

 continue feeding. 



There are other strong objections to the defect hypothesis. 

 Johnson (1893) independently discovered reorganization in 

 Stentor and he seems to have followed Balbiani's interpretation, 

 yet he described a case of two successive reorganizations in 

 coeruleus which cannot be explained on the improbable assumption 

 that the mouthparts just formed by the first primordium had 

 become defective through use or aging. Then Morgan (1901a) 

 noted that in most instances the old feeding organelles of re- 

 organizers are still active and appear entirely normal, though this, 

 he said, w^as not always the case. In my own studies, I talUed 36 

 cases in which newly-formed feeding organelles, wholly normal 

 in appearance, were promptly subjected to reorganizational 

 replacement, quite apart from the fact that in graft stentor com- 

 plexes repeated reorganization is the rule (Tartar, 1954). These 

 cases cannot be explained on the defect hypothesis unless one 

 supposes, against all appearances to the contrary, that the pre- 

 ceding differentiation was inadequate. 



If the mouthparts wear out, this should occur sooner in proters 

 which retain the old ones; yet Hetherington (1932b) did not find 

 reorganization in the continued isolation of proters for five 

 generations, i.e., of feeding organelles five generations old. Finally, 

 and most conclusively, one can specifically injure the mouthparts 

 by thrusting a needle down the gullet and cutting laterally, where- 

 upon the injury is simply repaired and no reorganization follows 

 (Tartar, 1957c) (see Fig. 33B). 



(b) Response to change in the medium? 



Hetherington (1932b) was strongly of the opinion that re- 

 organization does not occur in stentors under constant conditions 

 of culture, and that reorganization if it occurs at all, is brought 



\Uj I I IBRARY ]:>! 



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