SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 



713 



tained. Brody has discussed this phenomenon, which, of course, 

 appears very obtrusive when carbon dioxide output is calculated 

 Hke percentage growth-rate. They found it relatively easy to tell 

 whether the embryo had died, for in such cases an obvious falling 

 away from the rising curve appeared. Benjamin showed that, other 

 things being equal, the larger the egg the larger and more vigorous 



CC. 



350 



^300 



bo 



<u 



^250 



d 

 o 



1^200 



O 150 



O 

 o 

 ^ 100 



50 



•A 



2,2 2.4 ^6 2.8 3.0 3.2 3.4 3.6 

 Log weight of embryo 



Fig- 153- 



38 4.0 42 4.4 



the chick hatched therefrom (contradiction with Riddle's results on 

 pigeons (?) ; see p. 254), so Atwood & Weakley arranged their results 

 on carbon dioxide in a correlation table. They found that the correla- 

 tion was positive and significant, i.e. the larger eggs tend to give off 

 more carbon dioxide during the whole period than the smaller ones. 

 This would by no means have followed a priori. 



The most recent example of this kind of experiment is the work 

 of Murray. He only used eggs which had been allowed to come into 

 gaseous equilibrium with the air by standing in the apparatus for 

 some time before the experiment began, so he was able to leave out 



46-2 



