ACTIVATION OF STARFISH EGGS BY BUTYRIC ACID. 137 



perature in accordance 'with the usual temperature-coefficient of 

 reaction-velocities (<2io = 2 -- 3.5). The experiments described 

 below show that this is approximately the case for temperatures 

 between 8 and I8 ; 1 but with further rise in temperature the <2io 

 values increase at a disproportionately rapid rate, indicating the 

 entrance of some additional factor probably the direct influence 

 of the high temperature upon the egg-structure, as already indi- 

 cated. The rate of activation under the influence of heat alone 

 also increases very rapidly with rise in temperature (<2io = 200 

 400) . 2 Physical changes induced by heat in protein-containing 

 systems e. g., heat-coagulation or the melting of gelatine gels- 

 show similarly high temperature-coefficients; 3 so that it seems 

 probable that temperatures of the activating range (30 to 38) 

 produce their effects by altering the physical condition of the 

 structural colloids in the egg-system, and that this change secon- 

 darily facilitates or renders possible the chemical interaction 

 upon which activation depends. In order to account for the above 

 rise in the <2io values at temperatures above 20 it seems necessary 

 to assume that as the temperature approaches the region of 

 heat-activation proper, the physical conditions become pro- 

 gressively more favorable for the interaction of butyric acid with 

 the egg-component e. g., the resistance to the penetration of 

 acid is lessened so that the reaction is accelerated at a rate 

 higher than can be explained by the influence of temperature 

 upon reaction-velocity alone. 



A large number of experiments of the above kind were per- 

 formed between May 30 and June 28, 1916. During this period 

 at Woods Hole starfish eggs are abundant, and more uniform in 



1 Greeley (BIOLOGICAL BULLETIN, 1903, Vol. 4, p. 129) found with starfish 

 eggs exposed to a mixture of 5 c.c. w/io HC1 plus 100 c.c. sea-water an approximate 

 optimum at 23 of 5 minutes, at 11 of 15-30 minutes, and at 2 of 45-60 minutes. 

 This indicates for the action of HC1 a temperature-coefficient of a similar order. 

 Loeb and Hagedoorn found a similar coefficient for the production of fertilization- 

 membranes in sea-urchin eggs by butyric acid, the physiologically equivalent ex- 

 posures being twice as long at 10 as at 20 ("Artificial Parthenogenesis and Fer- 

 tilization," p. 146). The action of hypertonic sea-water shows a similar tempera- 

 ture-coefficient (cf. Greeley, loc. cit., pp. 131-133; Loeb, loo. cit;, p. 102). 



2 R. S. Lillie, BIOLOGICAL BULLETIN, loc. cit. 



3 C/. Schroeder, Zeitschr. f. physik. Chem., 1903, Vol. 45, p. 75; Levites, Kolloid- 

 ZeUschrift, 1907, Vol. 2, p. 211; Freundlich, " Kapillarchemie," 1909, p. 416; Chick 

 and Martin, Journal of Physiology, 1910, Vol. 40, p. 404, and 1912, Vol. 45, p. 261. 



