Whan the faOt th*t the water in *hich Woe. 2 and 3 actually remained contained 

 cuneiderably wore oxygen than was shown by the titrations ia taken into consider- 

 ation, thaaa eunraa (Fig. 34) show clearly a relation between regeneration ani 

 the oxygen content of the r iter. 



The aaaie thing is true of the medlua-aiaed tadpolea (TaMe 30, 

 Fig. 35). Of these Woe. 1 and 3 mala*! at the top and underwent regeneration. 

 Wo. 2, which did not show this rssponae, died without regeneration* Hoe. 4, 6 

 and 7, which remained at tho bottoa, undergo progra63ively better regane ration. 

 The dat* for the a:*all-ai*ed tadpoiea, 34 to 37 asm., are given .*t the bottom of 

 Table 30. Theee results are quite trpiosl of what occurred each tias an 

 attempt wee made to use 3**11 tadpoles in oxygen experiments. Woe. 1, 2 and 



3 regained at the top of the *ater. Woa. 2 and 3 lived twelve drays and underwent 

 alight regeneration. 3os. 4, 5, 6 and 7 stayed at the bottom, and of these 

 only Wo. 7 survived to undergo any regeneration, but its regeneration wee 

 apparently normal. 



Here again, as was thova for acids and bases, we find the suscepti- 

 bility of the tadpole as a whole as compared to the susceptibility of the 

 regenerating part ni$her in small 3 r tfeaa in larger tadpoles* 



The next series of axperiraanta waa csrried on in water kept basic 



to Rosalie acid and frooi acid to fcintly baaic to Phenolpthalsin. The teapers- 



turs waa alao oorrectsd Ly the introduction of the air cell which »*armed the 



water to air tempo ratura before it entered the e* nt J^ra. All of the 



tadpole* choeen were large an J showed rudintent-'.ry hind legs, as it was found 

 that tadpoles at thtt stage ror-sal' I the bottom of the Jar* better than 



thoae in earlier stages. The results (Table 31, Fig. 36) show an increase in 

 regeneration with an increase in Og content of the water with abrupt rises 

 bstweer. an! 0.7 c.c. per liter, and again between 3.68 and 4.1 c.c. par liter. 

 the following experiment still oldsr tadpoles were ueed. 



