ENVIRONMENT AND REGENERATION 497 



tadpoles and the abnormal behavior of others during the experi- 

 ment, no attempt was made to correlate the increase of CO2 

 production in bases or the decrease in acids with either weight 

 or area. The data show, on the whole, that the per cent increase 

 of COo production in bases and the per cent decrease in acids 

 both increase as the size of the tadpoles decreases. 



Child ('18) shows that in Gonionemus the effects of abnormal 

 hydrogen ion concentrations upon metabolism decrease as age 

 increases. In the majority of the author's experiments, however, 

 there was no indication that the tadpoles differed in age or near- 

 ness to metamorphosis, and the few tadpoles which did show 

 rudimentary hind legs did not differ appreciably nor always in 

 the same direction from the physiologically younger tadpoles 

 of the same size. Experience in rearing tadpoles shows great 

 variation in size in animals of the same age. In view of these 

 facts, it would seem that until parallel experiments can be per- 

 formed upon animals of the same size, but differing in age, and 

 of the same age, but differing in size, it must be regarded as an 

 open question whether the relatively greater effect of abnormal 

 hydrogen ion concentrations upon CO2 production in smaller 

 tadpoles may not be due simply to the relatively larger area 

 exposed to the unfavorable medium. 



The surviving tadpoles of the preceding experiment were 

 operated upon and allowed to undergo regeneration in the same 

 solutions as the CO2 determinations had been made for. The 

 concentrations used had no effect upon regeneration in the largest 

 size. The medium-sized tadpoles were affected only in the case 

 of H2SO4 in which regeneration was noticeably retarded, while 

 in the few of the smaller tadpoles which survived to regenerate 

 the regeneration was markedly depressed. 



A final series on the effect of size on regeneration was run in 

 30, 40, 50, and 60 cc. 0.01 N HCl made up to 1 liter in 10-inch 

 crystallizing dishes, each containing ten tadpoles of three distinct 

 sizes. Two controls were run. All of the tadpoles in the highest 

 concentration died without regeneration. Throughout the ex- 

 periment the smaller tadpoles showed a higher per cent of regener- 

 ation than the larger ones until a concentration was reached in 



