REGENERATION IN HYDRA ATTENUATA 



585 



ITN's, TRF's, FTN— ITN's are not significant. Thus, although budding animais 

 are slower to begin régénération, they achieve comparable or somewhat greater 

 quantities of regenerate at the end. Again, two animais from this group produced 

 a second set of buds. 



Table 8. 



Comparison of Week-Old Budding and Non- Budding Animais Transe et ed at 50% of 

 Total Length. 



TDT=Time of Tentacle Differentiation. FTN '= Final Tentacle Number. ITN= 

 Initial Tentacle Number. FTN — ITN = Final Tentacle Number minus Initial Tentacle 

 Number. TRF ^Tentacle Régénération Factor. N= Number of Animais Regenerated/ 

 Number of Animais Operated. 





TDT 



FTN 



ITN 



FTN— ITN 



TRF 



Budding 

 Animais 



N= 



81.80 ± 17.80 



5.63 ± 1.24 



1.50 ± 0.76 



4.13 ± 1.40 



300 ± 109 

 8/10 



Non- 



Budding 



Animais 



N= 



36.6 ± 4.13 



5.71 ± 0.69 



2.43 ± 1.23 



3.57 ± 1.72 



220 ± 54 

 7/7 



(d) Discussion 



The régénération performance of day-old standard budding animais differs 

 only slightly, if at ail from those of the non-budding controls as far as the number 

 and speed of increasing the number of tentacles are concerned, and here the 

 différence lies in favor of the budding animais. This may explain why TRF values 

 at 50% are often higher than at the adjacent levels since this is more or less the 

 vicinity of the budding région. (Buds are found at the following axial levels (basai 

 plate =0, hypostome=100%): young buds without tentacles 48% (N=32); 

 middle buds with short tentacles and beginning peduncle development: 43.5% 

 (N=32); old buds with ectoderm separated from parent animal but no apparent 

 basai plate: 39% (N=32)). In référence to the onset of tentacle differentiation, 

 day-old budding animais appear to demonstrate a consistent but small delay. The 

 shortness of the delay, the changing TRF at 50% and the fact that two animais 

 made a second set of buds, indicate that a theory based on the insufficiency of 

 available material is inadéquate. The fact that adjacent régions were not negatively 

 effected by the présence of the bud as far as the time of tentacle appearance is 

 concerned renders the notion of a diffusing inhibitor at least doubtful. The relative 



