490 MINNA E. JEWELL 



base to regenerate 20, 25, and 30 per cent, etc., of the amounts 

 removed be divided by the times required by the controls to 

 regenerate the corresponding amounts, the results will be approx- 

 imately the same. The inhibitory action of the base or acid is, 

 in general, no greater at one stage than at another. This is 

 similar to the findings of Krogh ('14 a) in his work on the devel- 

 opment of frog's eggs at various temperatures. 



Carbon-dioxide production and regeneration in acids 



The next series of experiments was undertaken to see whether 

 any correlation could be found between regeneration and carbon- 

 dioxide production in acids. Ten sets of four tadpoles each of 

 as nearly the same size as possible were used. The normal 

 carbon-dioxide production in distilled water for a period of three 

 days was determined after a two-day fast to allow the alimentary 

 tract to become empty. The first and tenth sets were then kept 

 in distilled water as controls, and the other eight put into 10, 

 20, 25, and 30 cc. of HCl and HBr made up to 400 cc. with distilled 

 water. The carbon-dioxide production, whether expressed as 

 cc. O.OIN H2CO3 per gram per day or as per cent of normal, 

 decreases progressively with the increase in concentration of 

 acids except in case of the tadpoles in 30 cc. of HCl (fig. 20) 

 which is probably not typical. The survivors were allowed to 

 regenerate in the same concentrations of acids, and again showed 

 a progressive decrease in regeneration from the lower to the higher 

 concentrations. Those in 25 cc. of acid showed very little 

 regeneration, and survived only eight days. 



The effect of the tadpoles upon the medium should be men- 

 tioned in this connection. It will be noted that although the 

 tit ratable acidity of the acid solutions (determined as Ba(0H)2 

 neutralized) becomes greater, due to the acids produced by the 

 tadpoles, the hydrogen ion concentration of the solution decreases. 

 It was furthermore noted, throughout all of the experiments, that 

 tadpoles in strongly acid solutions decrease greatly in size and 

 much more rapidly than those in strongly basic solutions, not- 

 withstanding the fact that the carbon-dioxide production of the 



