ENVIEONMENT AND REGENERATION 479 



of KOH upon the rate of regeneration taken as time necessary 

 to regenerate 20, 30, and 35 per cent of the amount removed. 

 The dotted line represents the average CO2 per gram per day 

 produced by the same tadpoles. It will be noted that the rate of 

 regeneration curves and the carbon-dioxide curve are not parallel. 

 This, however, would not be expected, as the normal carbon- 

 dioxide production is a straight line — that is, the amount of 

 carbon dioxide produced is practically the same from day to 

 day^ — whereas the normal regeneration (shown by the control 

 or dotted line in fig. 7) is a curve, increase in length of the regen- 

 erating part progressing more slowly as regeneration nears com- 

 pletion. It is of interest to note that the curve of regeneration 

 for the earliest stage shown (20 per cent of the amount removed) 

 corresponds more nearly to the curve of carbon-dioxide produc- 

 tion than does the curve for the second stage (30 per cent of the 

 amount removed), and this in turn shows more similarity than 

 does the curve for the third stage (35 per cent of the amount 

 removed). These facts suggest that at the very beginning of 

 the process of regeneration the retardation of regeneration 

 corresponds to the acceleration of oxygen metabolism, but that 

 later the two processes diverge progressively, due to the additional 

 inhibition to regeneration afforded by the presence of the regen- 

 erated tissue. 



In the next experiment six sets of five tadpoles each were used. 

 The normal CO2 production in distilled water of each set of tad- 

 poles was first determined for a period of six days, and used as 

 a basis of comparison for the CO2 production in KOH determined 

 for the five succeeding days. The tadpoles were then operated 

 upon and allowed to undergo regeneration in the same concen- 

 trations of KOH. Figure 9 gives the curves of regeneration of 

 the tadpoles which survived to undergo regeneration. Figure 

 11 compares the CO2 production expressed as per cent of normal 

 CO2 production (first dotted line) and as cc. O.OIN H2CO3 per 

 gram of tadpole per day (second dotted line) with curves repre- 

 senting the time required by the same tadpoles to regenerate 

 20, 30, and 35 per cent of the amounts removed in the same 

 concentrations of KOH. While these curves are not comparable, 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 30, NO. 4 



