REGENERATION IN HYDRA ATTENUATA 



575 



Table 3. 



ITN ( Initial Tentacle Number) . Mean number of tentacles initially observed in each 

 of four clones of standard animais at the various axial levels. Values omitted from statistical 

 régénération are in brackets. N= Number of Regenerated Animais. JBT=Just Below 

 Tentacles. 





Clone 7a ? 



Clone 6 $ 



Clone 18 6* 



Clone 3a Ç 



JBT 



N = 



2.96 ± 1.06 

 24 



2.54 ± 0.91 

 13 



3.20 ± 0.92 

 10 



2.93 ± 0.98 

 14 



75% 



N = 



3.28 ± 1.50 

 18 



3.13 ± 1.17 

 16 



2.58 ± 1-08 

 12 



2.70 ± 0.55 

 10 



50% 



N= 



3.28 + 0.79 

 21 



2.50 ± 1.26 

 13 



3.00 ± 0.48 

 13 



3.08 ± 0.77 

 12 



25% 



N= 



2.33 ± 1.13 

 15 



2.12 ± 0.88 

 8 



2.00 ± 1.16 

 10 



2.63 ± 0.64 

 8 



10% 



N= 



(1.00 ± 0.00) 

 3 



2.12 ± 0.64 

 8 



(2.00 ± 0.82) 

 4 



(2.33 ± 0.56) 

 3 



four levels; the différence for Clone 18 <J is significant at the 1 % level (F < 4.5) 

 and is apparently due to the extremely low value at the 25% level. By-and-large, 

 the values at the 25% level appear lower than those of the upper levels. A pooling 

 of the data gives the following weighted means : JBT : 2.05 ; 75 % : 1 .72 ; 50 % : 1 .66 ; 

 25%: 1.03; 10%: 0.70. Thèse figures appear to reflect something of a linear décline. 



However, at this point, attention must be called to the manner in which the 

 FTN — ITN value is established. The following also holds true for FTN évaluations. 

 Since régénération at the 25 % level begins some 20 hours later than that of JBT 

 and some 10 to 12 hours later than at the 50% and 75% levels, this value may be 

 artificially low. Further, both 75% and 50% levels have something like an 8 hour 

 disadvantage with respect to JBT; this last however, probably does not alter the 

 significance of the results at thèse levels since at thèse levels tentacle increase occurs 

 primarily in the first periods of protocol. 



5. The Tentacle Régénération Factor (TRF) 



In comparing the results which are given in Table 5, TRF's of zéro are 

 omitted since they obviously have no meaning in considérations of speed of 



