REGENERATION IN HYDRA ATTENUATA 



587 



(b) Materials and Methods 



1. Day-old animais from randomly selected mother animais 



Budding animais from several Stendor dishes were selected at random and 

 treated such as to obtain standard animais, as described in Section II, from them. 

 At séparation from their parent animais, the animais were each given either (1) 

 six units of food, (2) one unit of food, or (3) no food. Transection at 50% total 

 length occurred 24 hours after feeding. 



2. Week-old cloned animais 



Animais from Clone 3a Ç were pretreated in the usual manner and at time of 

 detachment from their parent animais were variously fed. Group la was given one 

 unit of food for six days, including day of séparation and transected 24 hours after 

 the last feeding at the 50% level. Group Ib was given six units of food at time of 

 detachment and operated on one week after séparation. Group le was given no 

 food for six days, and then fed six units of food 24 hours prior to transection. 

 Thus, week-old animais fed a total of six units of food are designated as Group I. 

 This group is compared to a second group of week-old animais: Group Ilb was 

 given one unit of food per animal at time of detachment and operated on one 

 week after séparation. Group Ile was left unfed for six days, and then given one 

 unit of food 24 hours prior to transection. Thus, animais fed a total of one unit 

 of food and transected on the seventh day after detachment are designated as 

 Group IL Groups I and II are then compared to a third group of week-old unfed 

 animais designated as Group III. Each of the above groups has a set of day-old 

 control animais given comparable quantities of food, i.e., Group IV l5 six units of 

 food; Group IV 2 , one unit of food and Group IV 3 , no food. Thus, ail day-old 

 animais are designated as Group IV. 



(c) Results 



1 . Day-old animais from randomly selected mother animais 



The data are given in Table 9. There is no significant différence with regard 

 to the onset of tentacle differentiation (TDT) nor for the Initial Tentacle Number. 

 Significantly différent, however, are the Final Tentacle Number (F=6.8, p < 0.01), 

 the FTN — ITN (F=6.6, p < 0.01) and the TRF's (F=4.8, p < 0.05), well-fed 

 animais reaching higher values. Thus, for thèse animais, apparently, only quantity 

 and speed of tentacle régénération could be significantly influenced by differential 

 feeding. 



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



39 



