412 Marion L. Durbin 
in Experiment IV have been explained as due to individual vari- 
ations after the series was reduced to eight, five and finally two 
tadpoles. The only example of a change in rate because of an 
a 
Ce) 
Fig. 6 Diagrams of the cross-sections of tadpole’s tail. A, Cross-section of the uninjured tail. B, 
Cross-section of the new tail after three days’ regeneration. C, Cross-section of the new tail after five 
days’ regeneration. D, Cross-section of the new tail after ten days. E, Cross-section of the new tail 
after fourteen days’ regeneration. 
n = notochord 
m = muscle 
= fin 
dorsal aorta 
ory, 
I 
= nerve chord 
irregularity in the aération of the water is in the last period of 
Experiment I. The water on the tadpoles was not changed for 
seven days, and at the end of that time the regenerated tail had 
shrunken .2 mm. and the animals all showed signs of ill health. 
