THE PROBLEM OF ACTIVATION 251 



ture, and this without interfering with the effect. 

 (2) Precisely similar quantitative relations obtain when 

 the same kind of eggs is activated by butyric acid at 

 normal temperatures, the variables being concentra- 

 tion and time in this case; and moreover it is possible 

 to complete an incomplete action of either temperature 

 or butyric acid by action of the other. There can thus 

 be no doubt that the processes of activation are the 

 same by these two methods. 



R. S. Lillie's conclusion is that the fundamental 

 " releasing " process in activation of the egg cannot 

 possibly depend on simple acceleration of some chemi- 

 cal process, such as oxidation, for the temperature 

 coefficient of such processes is of the order Q IO = 2~3, 

 instead of 200-400. There is some change in the nature 

 of degelation or decrease of viscosity in the cortical 

 layer which presumably allows substances to come 

 together and interact which in the condition of the 

 cortex of the unfertilized egg are kept apart. The 

 extent of the following development will depend on 

 the degree of completion of this process. This is of 

 course consistent with the idea of various authors that 

 the cortical changes release a specific catalytic action; 

 but R. S. Lillie's measurements of the releasing change 

 give us a much better idea of these changes than we 

 have previously had. 



Other theories of activation. The* veteran French 

 experimental zoologist Yves Delage (1908 and 1913; 

 earlier references here) has propounded a theory based 

 upon the conception that the phenomena of cell division 

 depend on a reversible series of gelations and degela- 

 tions in the protoplasm, changes from gel to sol and 



