SECT. 9] 



PROTEIN METABOLISM 



1 105 



Table 149. 



Terroine & Barthelemy Zero hour 



Faure-Fremiet & Dragoiu Zero hour 



Faure-Fremiet & Dragoiu Hatching 



Therefore lost during this time 

 Faure-Fremiet & Dragoiu Loss of yolk-sac 



Therefore lost during this time 



Lost during the whole time 



Protein 



Consumption of dry solid by amphibian embryos 

 10 20 30 40 



Evidently a good deal of the protein material with which the egg 

 begins is transformed into the protein of the larva, while a smaller 

 amount is combusted. Unfortunately Faure-Fremiet & Dragoiu did 

 not estimate the protein present at the last stage of all, and relied on 

 approximative assessment, but still their data give a general idea of 

 the process as a whole. 



The other investigators who have studied the chemistry of the 

 developing tadpole have for the most part paid no attention to its 

 protein metabolism. But a 

 notable exception is afforded 

 by the interesting paper of | 

 Bialascewicz & Mincovna 

 which appeared in 1921. 

 These workers estimated both 

 the nitrogen contained in the 

 embryos at different stages 

 and the nitrogen excreted into 

 the circumambient water on 

 each day. Bialascewicz & 

 Mincovna first established 

 the fact that some dry weight 

 is lost by the frog embryo — an important point, for earlier workers had 

 confused the issue by always expressing results in percentages. The 

 data are shown in Fig. 335, in addition to some others collected by 

 Bialascewicz himself in another paper, and by Galloway. Using 

 different temperatures, and consequently different hatching times 

 (68, 78, 90, 96, 100, 120 and 172 hours), Bialascewicz & Mincovna 

 found that the loss of dry solid was always practically identical at 



Days 5 10 15 20 25 30 



O Rana fu&ca (Bialascewicz) ©Rang sylvatical 



® " " (Bialascewicz S(Mcncovna) •Amblystoma flGalloway) 

 ® " •' (Barthelemy ^Bonnet) tigrinum ) 



Fig- 335- 



