10 



ILLINOIS BIOLOGICAL MONOGRAPHS 



[10 



Within each set the tail of tadpole 1 was removed at B (Fig. 1) 

 and the tail of tadpole 2 at A. The distance between A and B was 2 

 or 3 mm. After 21 days of regeneration the second operation on 

 both tadpoles came between A and B and therefore in old tissue in 

 tadpole 1 and in new tissue in tadpole 2. This procedure, insuring 



X B 



Figure 1. Outline of tadpole of Rana clamitans- Individuals used for re- 

 generation from old tissue have the original removal level at B and the second 

 level at A. Individuals used for regeneration from new tissue have the original 

 removal level at A and the second level at B. Regenerations from the second 

 levels are compared. 



approximately the same level in the two cases, is necessary because level 

 of the cut has a great influence upon rate of regeneration. Eleven pairs 

 of individuals weue used in the comparison. The precautions taken to 

 eliminate possible error are treated fully elsewhere for similar cases 

 (Zeleny 1909a, 1909b). 



The data are given in Table 1. The removed tail lengths are the 

 lengths of the original removed portions of the tail plus or minus the 



EXPLANATION OF TABLE I. 



Note 1. The removed length is the length of the original removed portion 

 of the tail plus or minus the distance of the new cut surface from the dividing 

 line between the old and new tissue. 



Note 2. The lengths as given are the living lengths. Measurements were 

 made on material killed in Gilson's mercuro-nitric mixture and preserved in 

 85% alcohol. Sets I and IX were measured both when alive and after killing 

 and preserving. From tljem the shrinkage coefficient was obtained and this 

 made possible the reduction of all the data to the living basis. 



Note 3. The specific amount regenerated in any case is the amount regen- 

 erated per unit of removed length. 



Note 4. The average includes only the sets in which both individuals are 

 present. 



