SECT. 4] HEAT-PRODUCTION OF THE EMBRYO 645 



phenomena. For, supposing that the carbon dioxide were produced 

 in the cell at a uniform rate just as the oxygen is apparently con- 

 sumed at a uniform rate, there might still be difficulties in observing 

 this. Nothing is yet known about the alkali reserve of the echinoderm 

 egg, and other factors, such as the alkalinity of the external medium 

 and the surface area of the egg, not accurately controlled in Vies' 

 experiments, might be expected to play a large part in conditioning 

 the results. "It is clear", said Gray, "that since the periodicity in 

 carbon dioxide output is not accompanied by a periodicity in oxygen 

 uptake, the former cannot be regarded as of significance in respect 

 to energy changes in the egg, unless they be due to some obscure 

 form of anaerobic activity for which there is no evidence." 



The smooth curve obtained by Gray for oxygen consumption of 

 eggs is in agreement with the earlier observations of Warburg, using 

 the Winkler method. It is a very important key position to have 

 gained, for in the light of it various theories which have been pro- 

 posed from time to time are stripped of some of their attraction. 

 Thus Matthews and Osterhout both claimed that the nucleus played 

 an active part in the oxidative mechanisms of the cell. This is an 

 old idea, and we have already referred to it in connection with the 

 "growth-catalyst". It was the basis of R. S. Lillie's work on intra- 

 cellular oxidations, and the association of ideas "nucleus-oxidations- 

 growth" lies at the bottom of much of Child's writing. Its influence 

 can be traced through region after region of investigation between 

 1900 and 19 1 8. Gray's work on the oxygen consumption of Echinus 

 eggs demonstrated that, if the nucleus had anything to do with 

 oxidations, its influence must be altogether independent of the phase 

 of nuclear activity, and must be unaffected by the presence or 

 absence of definite nuclear boundary. Again, Robertson in his book 

 suggested that differentiation and growth were dependent on the 

 relative concentration of some catalyst in the nuclear and cyto- 

 plasmic portions of cells. This autocatalyst being formed within the 

 nucleus can only enter the cytoplasm when the nuclear membrane 

 breaks down during each prophase. Robertson does not actually 

 say that the autocatalyst is an oxidising agent, but he accepts the 

 view that the presence of the substance can be gauged by the in- 

 tensity of cell-respiration. On Robertson's theory, therefore, rhythmic 

 changes during early embryonic development in the gaseous ex- 

 change would certainly be expected, and it is interesting that, 



