REGENERATION IN HYDRA ATTENUATA 



579 



Table 6. 



BDT (Time of Basai Plate Differentiation) . Mean time in hours of the first appearance 

 of functional basai plates a/ter transection in each of four clones of standard animais at 

 the varions axial levels. Values omitted from statistical considération are in brackets. 

 JBT=Just Below Tentacles. JAB=Just Above Basai Plate. N=Number of Animais 

 Regenerated/ Number of Animais Operated. Values are for régénérâtes only. 





Clone 7a ? 



Clone 6 ? 



Clone 18 



Clone 3a ? 



JBT 



N= 



(80.00+ 16.00) 



3/7 



(120.00) 

 1/7 



(96.00 + 5.12) 

 4/8 



0/8 



75% 



N= 



49.14 ± 11.68 



7/8 



46.00 ± 8.24 

 8/8 



43.00 ± 12.80 



8/8 



41.00+ 5.12 



8/8 



50% 



N= 



43.44 ± 7.09 

 7/7 



46.54 ± 11.44 

 11/11 



43.44 ± 4.24 



7/7 



36.00 + 4.25 



8/8 



25% 



N= 



36.86 ± 7.20 



7/7 



39.00 ± 7.59 

 8/8 



41.32+ 3.26 

 6/6 



42.28 ± 4.67 

 7/8 



10% 



N = 



32.00± 10.16 

 6/6 



40.00 ± 6.05 



8/8 



44.57 ± 12.00 



7/7 



37.00 - 9.44 



8/8 



JAB 



N= 



24.00 ± 6.92 



8/8 



28.57 ± 7.84 



7/7 



25.99 + 7.61 

 7/7 



26.00 ± 10.24 



8/8 



linear curves are described for hypostome and basai plate régénération, respectively. It is to be 

 noted, however, that only three levels for each type of régénération are compared. The intervais 

 between the three levels are not specifîcally defined, but do appear to be greater than those given 

 in this paper, thus precluding comparison. 



In another séries of noteworthy experiments cited in the same paper, the authors find that 

 basai plate and hypostome régénération times are differentially affected by the présence or absence 

 of hypostome and basai plate respectively. In brief, they find that the absence of hypostome 

 flattens out the time-of-basal-plate-regeneration curve by causing an accélération of basai plate 

 régénération at the two transection points farthest from the hypostome, at the same time causing 

 a delay in régénération at the transection point nearest the hypostome. In the absence of a basai 

 plate, hypostome régénération at each of the farthest transection points is delayed, while the 

 nearest point to the site of the basai plate is unaffected; the linear nature of the hypostome régéné- 

 ration curve, therefore, remains essentially unaltered. The authors interpret thèse findings to 

 mean that basai plate and hypostome are to some extent mutually inhibitory but do not offer an 

 explanation for the accélération of basai plate régénération when the transection point is close to 

 a hypostome. In agreement with those referred to above, Mookerjee and Bhattacharjee sub- 

 scribe to a theory of inhibitor and stimulator substances emanating from a physiological center of 

 activity in the hypostome, although their very interesting findings would appear to indicate that 

 the control and détermination of régénération must rest on a complexity of interacting factors. 



