ACTIVATION OF STARFISH EGGS BY BUTYRIC ACID. 133 



of reaction-velocities at ordinary temperatures is usually much 

 greater than that of diffusion; 1 hence if the simple rate of diffusion 

 into the egg is the essential factor determining the rate of acti- 

 vation, the effective times of exposure should be only slightly 

 altered by changes of temperature. On the other hand, if the 

 rate of entrance is itself unimportant, 2 and the essential action 

 of the acid consists in forming a chemical compound, the rate 

 of activation should be influenced by temperature in the manner 

 characteristic of chemical relations, i. e., doubled or tripled by a 

 rise of io. 3 



EXPERIMENTAL. 



In the experiments described below the rates of activation 

 have been determined for a considerable range of temperatures, 

 2 to 28 (with intervals of 2), using a single concentration of 

 butyric acid throughout, viz., .006 n in sea-water (6 c.c. n/io 

 acid phis 94 c.c. sea-water). In each series of experiments eggs 

 from the same lot usually taken from a single animal to insure 

 uniformity of condition were exposed simultaneously to this 

 solution at the two (or three) temperatures under comparison. 

 Usually in any single series two temperatures differing by 2 

 (e. g., 10 and 12) were chosen; sometimes three temperatures 

 were used, in case this could be done without interfering with 

 manipulation. The procedure was simple: the eggs, after wash- 

 ing thoroughly in sea-water, were placed in two (or three) small 



1 A list of temperature-coefficients of different physico-chemical properties and 

 processes is given in Snyder's paper, Amer. Journ. Physiol., 1908, Vol. 22, p. 309. 

 The values given for diffusion-processes are probably too high; Oholm, working in 

 Arrhenius' laboratory, finds for eight substances, including salts, alkalis and acids 

 (HC1 and CHsCOOH) Qio values ranging from 1.19 to 1.28. Cf. Oholm, Zeitschr. f. 

 physik. Chem., 1905, Vol. 50, p. 309 (cited in Lewis' "System of Physical Chemis- 

 try," Vol. i, 1916, p. 428). 



2 As would be the case if the rate of entrance were decidedly more rapid than 

 the rate of participation in the activation-process. 



3 This is the usual coefficient for the range of temperatures under consideration 

 in physiological processes. In general the Qw values for chemical reaction- velocities 

 decrease as the temperature rises; for a study of this phenomenon cf. Cohen Stuart, 

 Proceedings of the Royal Society of Amsterdam, May 23, 1912, p. 1159. Snyder 

 notes that in physiological processes a decrease of Qw at higher temperatures is also 

 frequently found (Amer. Journ. Physiol., 1911, Vol. 28, p. 167). In the activation 

 of starfish eggs by butyric acid, however, the reverse is the case, as will be seen 

 below. 



