()72 



('. M. LAPIERE AND J. CROSS 







Fig. 5. 



skin. 



400- TAIL FIN 



300 



200 



700 

 600 

 500 

 400 

 300 

 200 

 100 



Ax 



BACK SKIN I ^ 



I 



/ <» 



5 10 15 20 25 



HOURS AFTER PROLINE- H^ 



30 



Total radioactivity of hydroxyproline isolated from tail fin and back 



of newly deposited and old fibrils in this equilibrium state cannot 

 be established from the data. 



In the metamorphosing animal there was marked reduction in 

 total tail fin collagen, and diminished net incorporation, but a spe- 

 cific activity increment identical with the normal (up to 20 hours) 

 (Figs. 5 and 6). If the data (Fig. 5) for thyroxin-treated tail fins 

 were "normalized" to account for the loss of about 50 per cent dry 



