ACTIVATION OF STARFISH EGGS BY BUTYRIC ACID. 



hence escapes observation. The egg differs from the erythrocyte 

 in showing definite evidence of an incomplete reaction, but in 

 other respects the conditions in the two kinds of cell are alike. 



All of the conditions indicate that in activation as in cytolysis 

 the primary reaction takes place at the cell-surface. This view 

 is confirmed by the promptness with which the course of the 

 activation-process in butyric acid solution can be arrested at any 

 desired stage by a return to sea-water. It seems clear that com- 

 bination of the acid with some surface-component is concerned; 

 a difference of half a minute or less in the time of exposure to 

 .006 n butyric acid, especially at higher temperatures (24 and 

 over) may make all of the difference between incomplete and 

 complete activation, or between activar/on and destruction of 

 the egg. In its prompt initiation in the solution of acid and its 

 equally prompt arrest by return to sea-water the activation- 

 reaction resembles closely the type of response characteristic of 

 sensory structures like taste-buds or other chemical receptors in 

 normal chemical stimulation. Crozier has recently reached the 

 conclusion that in this case also stimulation is the result of a 

 chemical surface-interaction. 1 Here again the existence of a 

 far-reaching parallelism between the process of stimulation and 

 the activation of the egg-cell is indicated. It appears probable 

 that advance in the general physiology of stimulation will 

 furnish the key to the interpretation of the activation-process. 



The high temperature-coefficients of heat-cytolysis and of 

 heat-activation in eggs indicate clearly that alterations of certain 

 structural colloids of the cell lie at the basis of these effects. 

 Reactions are thus enabled to take place in the egg which in 

 some manner lead to the initiation of development. The initial 

 chemical reaction in heat-activation is probably simple in char- 

 acter and similar to that of acid-activation, as already suggested. 

 Apparently this reaction forms the condition of some definite 

 structural change in the egg-system; this change is followed by the 

 series of developmental changes. 



It is possible that an autolytic process may form the first step 



1 I. e., the time required for stimulation is much shorter than that required for 

 visible penetration of the acid into the cell-interior; cf. W. J. Crozier, Jour. Biol. 

 Chem., 1916, Vol. 24, p. 255; cf. pp. 2joseq.; Journal of Comparative Neurology, 1916, 

 Vol. 26, p. i. 



