SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 



677 



Bialascewicz & Bledovski next studied the intake of oxygen during 

 the early stages of development, and their results are shown in Fig. 1 29. 

 The curve rises smoothly during segmentation and gastrulation, etc., 

 but about the 150th hour attains a plateau. This plateau is main- 

 tained as long as the tadpoles are kept without food, but when they 

 begin to eat the respiration 

 rises in amount again. 

 Bialascewicz & Bledovski 

 rightly laid special stress on 

 their confirmation of War- 

 burg's results, in that the 

 respiration does not rise pari 

 passu with the increase in 

 general mass of nuclear sub- 

 stance. In absolute amounts 

 the values for oxygen intake 

 of Bialascewicz & Bledovski 

 are almost double those of 

 Godlevski, but all these 

 investigators agree in the 

 general upward trend of the 

 curve and the absence from it of the undulations found by Bataillon. 

 They found that the rising part of the curve, i.e. the plateau, could 

 be expressed by an equation for a parabola, before i.e. x^ kt^ + a, 

 where x is the amount of oxygen taken up by a given number of eggs 

 during time t, a the value for unfertilised eggs, and k a constant. This 

 rise then proceeds in a manner directly proportional to the square of 

 the developmental time. Bialascewicz & Bledovski applied the same 

 equation to the figures obtained by Meyerhof for the respiration of 

 the sea-urchin and by Bohr & Hasselbalch for the chick. In the case 

 of the frog, the constant was 0-0139, and the agreement between 

 observed and calculated values was very fair, as follows : 



50 100 150 200 250 



Hrs. after fertilisation 

 Fig. 129. 



^^ 



^/'t -*«^ 4^1 



