596 



GABRIELE KASS-SIMON 



VIL GENERAL DISCUSSION 



In view of the fact that régénération gradients do not completely coincide 

 with physiological data, it is perhaps necessary to emphasize that the animais used 

 here are of a very particular physiological state. This being the case, it still remains 

 to be seen whether physiological and/or cytological correlates can be found for 

 the régénération phenomena described. Discrepancies, as for example the relative 

 interstitial cell counts of Tardent (1952, 1954) and those of Campbell (1965) need 

 not necessarily be thought of as contradictory, or mutually exclusive, since it is 

 clear that animais with différent historiés give decidedly différent régénération 

 responses (Sections IV and V), especially at the exceedingly labile budding zone. 



Further, since notions of direct or competitory inhibition are not completely 

 satisfactory in explaining relationships between budding and régénération phenom- 

 ena, and since it is perhaps possible that excessive feeding rather than enhancing 

 régénération induces a ,budding condition' in the budding région which renders 

 that région incapable of responding to a régénération stimulus, the question of 

 budding and régénération still appears to require further investigation, especially 

 on a biochemical and physiological level. 



The same may be said in regard to feeding experiments, since the results for 

 day-old and week-old animais do not completely concur. Nor was there complète 

 agreement in results from cloned and uncloned animais under équivalent condi- 

 tions. It is therefore possible that more variables are involved than were controlled 

 in the experiment (e.g. parental nutritional history) or that a one to one relation- 

 ship between Food and Régénération does not exist. No définitive statements, 

 therefore ought to be made about the effect of feeding on régénération until 

 physiological variables are under complète control. 



Finally, although results indicate that the differential régénération exhibited 

 by distal and proximal halves of Hydra attenuata may be due to différences in the 

 présence, synthesis and/or dégradation of RNA during régénération of basai plate 

 and tentacles, respectively, the question must remain open for investigation at the 

 cellular level. 



SUMMARY 



1. There are inhérent significant différences in the régénération performance 

 of the various axial levels which do not stand in ranked relation to one another 

 in a steadily declining gradient. Basai plate and tentacle régénération do not 

 reflect complementary régénération gradients. 



2. Except for the budding région, no différence in onset of tentacle régénéra- 

 tion was found between budding and non-budding animais, although a relative 



