132 RALPH S. LILLIE. 



conditions in the egg-system, until a certain definite quantity of 

 reaction-product is formed ; this is the critical quantity required to 

 enable the egg to continue its development to an advanced stage; 

 and if the reaction is then arrested by returning the eggs to sea- 

 water, activation is found to be complete and development con- 

 tinues normally. If, however, the exposure has been too brief, 

 so that the quantity of reaction-product formed is insufficient, 

 activation is only partial and development ceases at an early 

 stage. Similarly, over-exposure leads to an excessive accumu- 

 lation of the reaction-product a condition also unfavorable to 

 devf'opment. According to this hypothesis, the activation- 

 process consists essentially in the production of a definite reaction- 

 product, which may be called the activating substance. Since 

 the rate at which the butyric acid takes part in the process is 

 directly proportional to its concentration, it is evident that the 

 interaction has the character of a monomolecular reaction: i. e., 

 the product of the concentration into the time required to produce 

 a given quantity of reaction-product is constant (qt = const.). 

 The quantity of egg-constituent transformed into activating 

 substance in unit time is a direct linear function of the concen- 

 tration of butyric acid. 1 



Some further test of this hypothesis has seemed desirable, 

 since the objection is possible that the activating effect depends 

 simply upon the entrance of a certain critical quantity of acid into 

 the egg. According to the general law of diffusion, the rate of 

 such entrance would be proportional to the difference in the con- 

 centration of acid between medium and cell-interior; hence the 

 time required for the entrance of the activating quantity of acid 

 ought to vary inversely with its concentration in the medium. 

 No inference as to the mode of action of the acid would then be 

 possible from the above facts alone. A possible means of de- 

 ciding between these alternatives lies in determining the manner 

 in which the rate of activation in a given solution of acid is in- 

 fluenced by change of temperature. The temperature-coefficient 



1 The destruction of an inhibiting substance by combination with the acid might 

 be supposed to underlie the activation effect, but in this case the rate of destruction 

 would not be uniform, but would fall off with the progressive disappearance of the 

 ;nhibiting substance. All of the evidence indicates that the rate of activation is 

 uniform and a direct function of the concentration of acid. 



