SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 



667 



Fig. 125 shows the undulatory curve which she obtained in her 

 experiments, with peaks at 2, 4 and 10 days after fertiHsation. The 

 values, it will be noted, are of the same order as Scott & Kellicott's. 

 The segmentation stages were all passed through during the first 

 upward rise of the curve, which reaches its peak at the time when 

 the morula stages (though the term is inappropriate for a teleostean 

 have all been passed through, and the shape of the embryo 



50 



40 



c 20 - 



o 

 O 10 



0«20 



-0«1 



0*05 



Fert. 



appears clearly for the first time. Just prior to this point, the germ 

 ring has been approaching the equator of the egg, and what corre- 

 sponds to gastrulation has been proceeding. After this time, there 

 is apparently a fall to the point at which the heart begins to beat, 

 but thereupon a rapid rise takes place, which is presumably the same 

 as that referred to by Scott & Kellicott in connection with active 

 circulation. Later values are described by Hyman as "irregular", 

 but when the actual figures she gives are plotted on the same graph 

 they only show a gradual fall, followed by a gradual rise. It is to 



