158 ILLINOIS BIOLOGICAL MONOGRAPHS [158 



PART VI 



THE COMPLETENESS OF REGENERATION 



One of the striking facts in connection with amphibian regeneration 

 as made out in the present studies is the lack of completeness of the 

 process. When a part of the tail is removed the lost part is never com- 

 pletely restored. Data on this problem are to be found in a number of 

 sets of experiments one of which (Experiment V) was devised especially 

 for the present purpose. 



Experiment I Rana clamitans Series 3557-3624 



One-half of the tail was removed in the individuals of three groups, 

 A, B and C. After 35 to 39 days, which was sufficiently long so that 

 regeneration had stopped, another removal was made and so on until each 

 individual had undergone five regenerations. The data are given in 

 Table 104. The average removed length as estimated from the measure- 

 ment of a few individuals was 17.0 mm. The average length of the com- 

 pleted first regeneration is 8.6 mm. or 51 per cent of the removed length, 

 of the second regeneration 8.0 mm. or 53 per cent, of the third 7.5 mm. 

 or 51 per cent, of the fourth 5.5 mm. or 42 per cent and of the fifth 

 6.4 mm. of 45 per cent. On the average about one-half of the removed 

 length is replaced when one-half of the tail length is removed. 



Experiment II Rana clamitans Series 3628-3675 



One-half of the tail length was removed in the individuals of this 

 experiment and regeneration was allowed to proceed for twenty days, 

 a sufficient time for bringing it to a stop. The data are given in Table 

 105. The average original tail .length was 21.8 mm., of the removed 

 length 10.6 mm. and of the regenerated length 5.4 mm. The completed 

 regenerated length is thus 51 per cent of the removed length. 



Experiment III Rana clamitans First regenerations 

 Series 3676-3765 



The data are given in Table 106. The tails were removed at different 

 levels approximating 6, 10, 17, 30, 48 and 62 per cent of the tail lengths. 

 Regeneration was completed at these levels at 12^2, 12%, 12V2> 18, 18 



