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ILLINOIS BIOLOGICAL MONOGRAPHS 



[54 



and for the third 1.80 ^0.03 mm., a difference in favor of the first re- 

 generation of 0.14 ± 0.05 mm. This represents a regeneration of 0.51 mm. 

 per unit of removed length in the first regeneration and 0.47 mm. per 

 unit in the third regeneration. A comparison of individual cases shows 

 that the first regeneration is ahead of the third in 36 individuals, the 

 third is ahead of the first in 18 individuals and 5 are tied. The differ- 

 ence between the two regenerations is thus probably significant. As in 

 Experiment V the decrease is probably due to the age factor. 



The second regeneration has a time interval of ten days, one day 

 more than the first and third regenerations. In the absence of know- 

 ledge concerning the rate curve for toad tadpoles of this age no cor- 

 rection can be applied. The rates per day for the three regenerations 

 are however given in the table. 



TABLE 35 

 Bufo americanus Series 6283-6323 Age factor not eliminated 

 Successive regenerations of tail 



