19. 

 normal rate up to a certain point and w*s than discontinued abruptly. The 

 HgPC^ aerie* of experiment 8 (tsble 13, fig. 18) gave »imil%r characteristic 

 curves, but why the form of the HgP0 4 curve should differ from th*t of the other 

 eeide is not explained. Twelve an! one-half e.o. O.Ol Iff HSr or H2SO4 gives 



about the ease initial hydrogen Ion concentration as twenty-five o.c. 0.01 mol. 

 H3PO4 beeauae of it a greater ionization, but by the end of twenty-four hount 

 the hydrogen ion concentration la -rue'; lower. This la beeauae the total 

 number of hylrogen ions whioh must be replaced before the solution will be 

 neutral is greater in the H3PO4 , consequently it is neutralized more slowly. 

 Thus the tadpoles |sj the stronger acids are in a medium of higher hydrogen ion 

 concentration each time the solution is changed but of lower hydrogen ion 

 oonoentration before it io changed again than those in tfta H3PO4, that lm, they 

 live under a more variable enviroutaorit. Further experiments till be needed 

 fcfj sho« whethsr this is the oauae of the difference in ths regeneration curves 

 or whethsr it is caused by some specific action of the HJPO^. 



The tadpoles marked (T) (Tables 15, 16 and 1?) *ere transferred 

 to neutral distilled water to see whether normal regeneration could take plc-.ce 

 after the* initial stunting vith acids. Their subsequent regeneration is, 

 of course, not added in with the vtlMr tadpoles of th* group in determining 

 the p*r cent of regeneration. Tadpoles tranaferred luring the first days of 

 the experiment underwent more regeneration thar; those i«»ft in the solutions but 

 their regeneration was far below normal. At the close of the experiment all 

 survlvoro were transferred to distilled water but none of them underwent further 

 regeneration, showing that the effect of adds is not merely a retardation but 

 a permanent inhibition to regeneration. 



The ourvee in figure 25 represent the time required to regenerate 

 ?2.5£ of the amount retrove.1 in HHO3 and 25# of the amount removed in HBr, 



