ENVIRONMENT AND REGENERATION 



485 



HBr, and in HBr than in H2SO4. The data are, however, insuf- 

 ficient to warrant any conclusions. In H3PO4 (fig. 6) there was 

 no such marked retardation of regeneration in the concentrations 

 used, although the decrease in the total amount regenerated 

 was equally pronounced. Regeneration proceeded at very 



Fig. 13 Graph showing the regeneration of tadpoles in increasing concentra- 

 tions of HNO3. Each line, average regeneration of four tadpoles; dotted line, 

 control; ordinate, per cent regenerated; abscissa, time in days; numbers at ends 

 of curves, cc. O.OIN HNO3 in 200 cc. of solution. Compare with figures 6, 15, and 17 

 for regeneration in H3PO4, HBr, and H2SO4. 



Fig. 14 Graph showing retardation of regeneration in increasing concentra- 

 tions of HNO3. Dotted lines, experimental data; soZid h'nes, theoretical curves; 

 ordinate, concentration as cc. O.OIN HNO3 in 200 cc. of solution; abscissa, time in 

 days; numbers at ends of lines, per cent regenerated. These curves were plotted 

 from the same data as figure 13. Note that the curves are roughly confocal, 

 showing that the relative retardation for each concentration is the same for the 

 three different stages represented. Compare with figures 8, 11, and 12. 



Fig. 15 Graph showing the regeneration of tadpoles in increasing concentra- 

 tions of HBr. Plotted as figure 13. These tadpoles were slightly larger than 

 those in the HNO3 experiment. 



Fig. 16 Graph showing retardation to regeneration of tadpoles in increasing 

 concentrations of HBr. Plotted as figure 14, from the same data as figure 15. 

 These curves also are roughly confocal, indicating the same relative retardation 

 for each concentration at the three different stages represented. 



