TEMPERATURE-COEFFICIENTS IN THE ACTIVATION 

 OF STARFISH EGGS BY BUTYRIC ACID. 



RALPH S. LILLIE. 



(From the Marine Biological Laboratory, Woods Hole, and the Physiological 



Laboratory, Clark University) 



INTRODUCTORY. 



In experiments performed at Woods Hole during the summers 

 of 1915 and 1916 it was found that unfertilized starfish eggs may 

 be completely activated so that with normal eggs 95 per cent, or 

 more form blastulae by a single exposure to a weak solution of 

 butyric acid (in sea-water or Van't Hoff's solution) at room tem- 

 perature. 1 To secure this result with a given solution of acid all 

 that is required is that the duration of the exposure should be 

 definite within somewhat narrow limits. Exposures briefer than 

 this optimum cause incomplete activation, which may fail to 

 carry the egg beyond membrane-formation and a few early 

 cleavages; in such cases the activation may be completed and the 

 egg rendered capable of advanced development by a second prop- 

 erly timed exposure to the same solution. Over-exposure 

 directly injuries the eggs and impairs or destroys their power of 

 development. Corresponding to each concentration of acid 

 within a wide range (.0005 n to .006 ) there was found a well 

 defined optimum duration of exposure; this duration was approxi- 

 mately inversely proportional to the concentration of acid. 



These facts, especially the direct proportionality between the 

 concentration of acid and the speed of the activation- process, 

 indicate that a chemical interaction between the acid and some 

 unknown egg-constituent (probably surface-component), rather 

 than a purely physical effect, is the critical or determinative event 

 in this type of activation. Apparently during the period of ex- 

 posure this interaction continues uniformly, at a rate determined 

 by the temperature, concentration of acid, and the structural 



1 BIOLOGICAL BULLETIN, 1915, Vol. 28, p. 260; Journ. Biol. Chem., 1916, Vol. 24, 

 P- 233. 



