8 Ada Springer 



The injured sets Normal control sets 



(i) Set £1 (Table V) i4-7 Set G' (Table V) 11.4 



(2) Set £2 (Table V) 10.5 Set G^ (Table V) loss - 1.2 



(3) Set £3 (Table V) 14-2 Set G3(Table V) 6.5 



The average for the injured sets is 13. i percent increment, 

 and for the two normal control sets, in which there was a gain, 

 8.9 per cent increment. 



After a period of fourteen weeks Set E^ had gained 47.7 per 

 cent, while the normal set had gained 44.6 per cent. 



Set E^ (Table V), in which the new tails had been regenerating 

 for five weeks, was divided, December 18, into two sets of five 

 individuals each. In one set, E^^ (Table VII), the animals were 

 again injured by cutting off the regenerating stump, together 

 with a small piece of the old material at the base of the tail; in 

 the other set, E^*" (Table VII), the regenerating stumps were left 

 intact. This latter set, together with the normal intact Set G* 

 (Table V), were used as controls. The results after a period of 

 four weeks were as follows. 



Increment 

 per cent 



Set E''^, injured animals (average) 21 . 



Set E'^, animals with regenerating stumps 5-4 



Set Gi, normal intact animals n -4 



The same experiment was duplicated by dividing Set E^ (Table 

 V) in the same way as Set E^ the two being equivalent sets. The 

 results were correspondingly the same (Table VIII): 



Increment 



average 

 per cent 



Set £2*, injured animals ^i -3 



Set E-^, animals with regenerating stumps 18.2 



Set G', normal intact animals 1 1 • 4 



The percentage increment, or the rate of growth in the injured 

 set in both cases, was greater than in the normal control or in 

 those with regenerating stumps. 



Three other experiments, also started on December i8, resulted 

 in similar comparative percentage increments. Two sets which 



