J. R. GREGG 



249 



than half of it left; while hybrid embryos (Fig. 11) seem to uti- 

 lize their carbohydrates at a slow, almost constant rate through- 

 out their development from Stage HI to Stage H21. The fact that 

 embryos of both types use their glycogen and their total carbo- 



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DEVELOPMENTAL STAGE OF CONTROLS 



21 



Fig. 11. Endogenous carbohydrate of developing hybrid embryos. Up- 

 per curve, total carbohydrate; middle curve, glycogen; lower curve, free 

 carbohydrate. (From Gregg, 1948.) 



hydrate at similar rates suggests two things: (a) that glycogen 

 is the only stored carbohydrate oxidized in any great amount 

 throughout embryonic development, and (b) that there is no 

 conversion of glycogen into any other stored carbohydrate — a 



