548 



ON INCREASE IN COMPLEXITY 



[PT. Ill 



older the embryo. A note of caution must be inserted here, how- 

 ever, in view of the fact that, until we know more about the behaviour 

 of individual organs in the light of these conceptions, we cannot 

 estimate the part played by ossification, for instance, in producing 

 these overall results. Murray also afterwards found that the curve 



Per Pep 

 cent cent 



9 11 13 



Incubation age 

 Fig. 92. 



relating age with oxygen absorbed by the embryo per gm, per day 

 did not decline quite like the carbon dioxide evolution curve, i.e. 

 slowly at first, and then quicker and quicker, but was rather S-shaped, 

 the slowest rate occurring at the loth day. His line for this, how- 

 ever, depended for the initial fall exclusively upon one very high 

 point for the 6th day, and this may quite possibly have been wrong, 

 in which case the curve for oxygen consumption would fall with the 

 curve for carbon dioxide output. 



