12. 



A comparleon of tablss 1 and 2, *>n •! 3 and 4, brings out anothsr 



int»r*stln£ point: That the lRrgor tadpoles (tables 1 and 3) ahow a marked 



retardation of regeneration In 15 and 20 o.o. of the baeea, while the smaller 



tadpoles (tablaa 2 and 4) ore killed by concent rations which produce reach lata 



retardation of regeneration. Th*t while the norwnl regeneration of the 



smaller tadpolee 1b much faster than thst of the larger ones, the effect of <»ny 



srivsn concentration of baae on regeneration le about the same for both slsss, 



being, if anything, more marked la the larger individual while the effect upon 



the animal ae a whols, aa shown by the length of life, is greater in case of 



the smallsr individual. Frorc this we say believe thnt while regeneration is 



affsoted by tne ea«e agents as general metabolism, the two vary independently 



and that the thrasholl of toxicity (Powers 1918 b) of a substance to the 



regenerating tissues may be above or b^iio* th* threshold of toxicity to the 



organism as a whols. This subject of the effect of else upon Regeneration 



and Metabolism will be more fully discussed l»ter. 



Tho next series of oxrjsriaents (Tables 5,5a and 6. Figures 5, f, 



7 and 8) was run in order to determine whether the effect of bau»as upon regener- 

 ation was due to the action of the hydroxyl lone or whether the ketions or 

 osmotic prsesuro played an important part. 0. 1 raol. solutions of NagCOa 



and KaHCOg were used. The nuaber of o.c. of tho solution used is given in 

 the first colusm. Thin was amis up to two hundred c.c. with distilled water. 

 The experiments were carried on In finger bowls, each containing four tadpoles, 

 and the water was changed alternate days* 



In order to assure a uniformity of slae of tadpoles in the various 

 solutions, the eighty tadpolas used were first divided into four lotu, such 

 lot containing tadpolos of a uniform slae. One taipola from auch of the four 

 lots was then put into eaoh of the solutions. Thla method for obtaining 

 uniformity of six* was ueod in all suooeeding experimante where a large number 



