ENVIRONMENT AND REGENERATION 



495 



The next series was carried out in the same manner. Carbon- 

 dioxide production was determined over a period of eight days. 

 It was noticed during this experiment that the large tadpoles 

 frequently exhausted the oxygen from the air in the experimental 

 jars. This was evident because when the jars were opened, 

 although the temperature had remained constant, the lids came 

 off with a 'pop/ showing that a partial vacuum had been formed. 

 The tadpoles also had a tendency to float at the surface as they 

 had been observed to do in low oxygen water. For this reason 

 it was rather to be expected that the CO2 production of the larger 

 size would be proportionately low, and this was found to be the 

 case as the following table shows : 



When, now, the large tadpoles, whose CO2 production was 

 limited by insufficiency of oxygen, are taken as standard or 100 

 per cent in comparing the area, weight, and CO2 production of 

 the three sets, the CO2 production of the second and third sets 

 appear abnormally high. Despite this fact, however, the CO2 

 production still corresponds more nearly to weight than to area, 

 especially in the third size. 



At the close of the eight days in distilled water the CO2 pro- 

 duction of the same tadpoles was determined for a period of 

 six days in 0.0005 N HCl (20 cc. 0.01 N in 400 cc). The CO2 

 production decreased in all three sets. Although the absolute 

 decrease was greater in the larger tadpoles the relative decrease 

 was greater in the smaller ones, the per cent of decrease as com- 

 pared to normal being 38 per cent, 48 per cent, and 50 per cent 

 in the large, medium, and small sizes, respectively. 



the journal of experimental zoology, vol. 30, no. 4 



