ACTIVATION OF UNFERTILIZED STARFISH EGGS. 28l 



depends on some critical change in the egg which does not 

 begin until a temperature of about 29° is reached, but which 

 undergoes very rapid acceleration with further rise of tempera- 

 ture. The liquefaction of gels by heat seems to be the only 

 relevant process which shows these characteristics. The change 

 in viscosity preceding the gelation of a gelatine sol undergoes 

 very rapid acceleration with lowering of temperature, within a 

 few degrees of the temperature of gelation. The inverse process, 

 melting of gels, has a similarly high temperature-coefhcient {cf. 

 below, p. 295). In general the facts suggest that the direct effect 

 of the high temperature is to cause a change in the colloidal 

 system of the egg, of such a kind as to render possible a chemical 

 interaction between substances which in the normal condition 

 of the resting egg are kept apart. *This restraining condition 

 may be some physical barrier like a membrane, impermeable to 

 the diffusion of the substances concerned, or it may be a certain 

 state of electrical polarization of the general cell-surface, as 

 suggested below (p. 299). It is also important to note that the 

 activation-process may be arrested by a return of the eggs to 

 sea-water at ordinary temperatures, and renewed after an interval 

 without interfering with its effect. A reversibility of the physico- 

 chemical change forming its basis is thus indicated. It should 

 further be noted that cytolytic agents like butyric acid not only 

 have the same general physiological effect as brief warming, but 

 that the relations between time of exposure and physiological 

 effect produced are the same in both cases. Some process which 

 is affected similarly by these two dissimilar agents is thus to be 

 sought. In the following section the results of experiments with 

 weak butyric acid solution are described in greater detail. 



Effects of Exposure to Butyric Acid Solution for 

 Different Periods. 



As already stated, treatment of starfish eggs during the early 

 maturation period with weak solutions of butyric acid in sea- 

 water (w/260) produces the same effects as temporary warming, 



Archivf. d. ges. Physiologic, 1908, Vol. 124, p. 411; A. R. Moore: Quarterly Journal 

 of Experimental Physiology, 1910, Vol. 3, p. 257; Arch. f. Entwicklungsmech., 1910, 

 Vol. 29, pp. 146, 287. 



