REGENERATION IN HYDRA ATTENUATA 



571 



number of tentacles initially observed (ITN), and the increase in tentacle number, 

 i.e. the différence between the two (FTN-ITN) and by a tentacle régénération 

 factor (TRF). (See pages 569 and 570). 



(b) Material and Methods 



Standard animais, as defined in Section II, were transected at Just Below the 

 Tentacle Ring (JBT), 75%, 50%, 25%, and 10% levels for hydranth régénération 

 and judged according to the given criteria. In addition, animais were sectioned at 

 Just Above the Basai Plate for basai plate régénération. When fewer than 5 animais 

 regenerated at a given level, that level is omitted from the statistics. 



(c) Results 



1 . Time of Tentacle Differentiation (TDT) 



The data are given in Table 1, and since no significant différence was found 

 among the four clones at any given level, the means of the weighted four clone 



Table 1. 



TDT (Time of Tentacle Differentiation) . Mean time in hours of the first appearance 

 of tentacles after transection at the various axial levels in each of four clones of standard 

 animais. Values omitted from statistical considération are in brackets. JBT = Just Below 

 Tentacles. N= Number of Animais Regenerated/ Number of Animais Operated. Values 

 are for régénérâtes only. 





Clone 7a ? 



Clone 6 Ç 



Clone 18 <S 



Clone 3a $ 



JBT 



N = 



28.80 ± 5.68 

 25/25 



30.79 ± 5.13 

 13/13 



29.60 ± 3.86 

 10/10 



27.70 ± 6.90 

 15/15 



75% 



N= 



33.42 ± 10.24 

 21/21 



38.48 ± 5.15 

 16/16 



36.00 ± 4.18 

 12/12 



34.00 ± 6.93 

 12/12 



50% 



N = 



32.40 ± 3.98 

 21/21 



36.23 ± 4.98 

 17/17 



34.00 ± 4.62 

 16/16 



32.00 ± 4.82 

 12/12 



25% 



N = 



42.29 ± 4.70 

 20/20 



47.00 ± 3.25 

 9/11 



55.20 ± 5.40 

 10/11 



40.00 ± 0.00 

 8/10 



10% 



N = 



(84.00 ± 4.60) 

 3/10 



48.00 ± 4.13 

 7/10 



52.80 ± 8.00 

 5/10 



92.00 ± 17.20 

 5/10 



Rev. Suisse de Zool., T. 76, 1969. 



38 



