23] 



RATE OF REGENERATION —ZELEN V 



23 



specific rates of regeneration can not be calculated. However the re- 

 moved lengths were so nearly alike as to make the regenerated lengths 

 of value in direct comparison. 



The data are given in Table 18. The average length of the 

 third regeneration is 7.9 mm. for both the old and the new tissue 

 basis. For the fourth regeneration the value from old tissue is 

 5.3 mm. and from new tissue 5.5 mm. The corresponding values 

 for the fifth regeneration are 6.6 mm. and 5.9 mm. Averaging 

 the individual cases for all three regenerations the old tissue average 

 is 6.5 mm. and the new tissue average 6.6 mm., an advantage in 

 favor of the latter of 0.1 mm. This difference can not be consid- 

 ered as significant, especially since for the individual regenerations 

 the two levels give equal regenerated lengths for the third, the new is 

 slightly ahead at the fourth and the old is ahead at the fifth. 



On the whole the data for Experiment III agree with those for 

 Experiments I and II. There is no striking difference between com- 

 pleteness of regeneration from old and from new tissue levels, though 

 a small difference favoring the latter persists in practically all the 

 comparisons. 



TABLE 18 



Rana clamitans Series 3557-3624 



Regenerated tail length from new tissue compared with that from old tissue 



during the third, fourth and fifth regenerations 



