ENVIRONMENT AND REGENERATION 



501 



Fig. 21 Graph showing the regeneration of tadpoles in increasing concen- 

 trations of oxygen. Each line represents the regeneration of one individual 

 tadpole. Numbers at the ends of lines correspond to position in the series of 

 increasing oxygen content (table 7). Ordinate, five regenerated; abscissa, time 

 in days. From data of table 7. 



Fig. 22 Graph showing the regeneration of tadpoles in increasing concen- 

 trations of oxygen and the result of aerating the water before the completion of 

 regeneration. Plotted as figure 21. Dotted line indicates the time at which 

 the water became aerated. 



Fig. 23 Graph showing the time required to regenerate 20 per cent of the 

 amount removed in increasing concentrations of oxygen. Ordinate, cc. oxygen 

 per liter; abscissa, time in days. From data of table 7. Since regeneration 

 increases with concentration of oxygen and decreases with increase in concen- 

 tration of bases and acids, this curve is the converse of the retardation of regen- 

 eration curves shown in figures 8, 11, 12, 14, 16, and 18, although plotted the same. 

 It conforms quite closely to an equilateral hyperbola with its zero a minus 

 amount of oxygeuz 



Fig. 24 Graph showing the regeneration of tadpoles in increasing temperatures. 

 Each line, average of four tadpoles; ordinate, per cent regenerated; abscissa, 

 time in days; numbers on curves, temperature centigrade. From data of table 8. 

 The tadpoles transferred from the lowest temperature (0° to 4°) on the thirtieth 

 day undergo a regeneration parallel to those put at room temperature immediately 

 after operation. The regeneration is, however, not so complete. 



