SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 



635 



using manometric methods instead of the Winkler titration. He first 

 obtained a more accurate figure for the oxygen utiHsation of sperma- 

 tozoa, namely, 66 c.mm. oxygen per 20 mgm. nitrogen in 20 minutes 

 at 23°. On the other hand, 20 mgm. egg nitrogen used 10-14 c.mm. 

 oxygen in 20 minutes at 23°. Warburg found that the rise occurring 

 at fertilisation took place within 10 minutes, during which time the 



egg 



6 8 10 12 14 16 18 20 

 Hours after ferfcilisafcion 

 Fig. 108. 



22 24 



respiratory rate rose six times. In the course of further development 

 it continued to rise, so that, after 6 hours, it had reached twelve times 

 the value of the unfertilised egg, after 1 2 hours sixteen times, and after 

 24 hours twenty- two times. Warburg's curve, which is reproduced in 

 Fig. 108, is very regular, and shows no peaks or rhythmic changes. 



For the gaseous exchange of the fertiHsed Strong^locentrotus egg^ 

 respiratory quotients closely distributed around o-g were found ^. 



1 Values of unity both before and after fertilisation were later reported for echinoderm 

 eggs by Ashbel. 



