296 RALPH S. LILLIE. 



at the lower temperatures there is a steady increase. If we 

 take comparatively short time intervals, e. g., 10 minutes, we 



find that the value of Arj/At at 21° ( ^^ ^^ = 0.062 ) is 



about seven times greater than at 24.8° I '- — = 0.009 ) • 



In other words, a difference of about 4° increases the average 

 rate of the gelation-process from six to seven times. What is 

 true of the gelation-process is also true of the inverse degelation 

 or melting process, whose rate increases at a similarly rapid rate 

 with rise of temperature above the critical maximum at which 

 the system remains permanently in the gel state. ^ 



In starfish eggs the rate of the activation-process, at tempera- 

 tures between 30° and 36°, shows a similar proportionate increase 

 with a given rise of temperature, as will be seen by reference 

 to Table X.; i. e., the temperature-coefficients of the two proc- 

 esses, gel-sol transformation, and activation of the egg under 

 the influence of high temperatures, are similar in their order 

 of dimensions; thus a rise of 4° shortens the time of exposure 

 necessary to cause membrane-formation or development by six 

 to ten times. On the assumption that some specific chemical 

 interaction is the essential change in the initiation of develop- 

 ment, such a result indicates that the rate of this interaction is 

 dependent, in the case of parthenogenesis by warming, on the 

 rate of some process involving either degelation or decrease in 

 the viscosity of some portion of the colloidal system of the egg. 

 This is as much as can be inferred on the basis of these facts alone. 

 If we also take into account the other methods by which mem- 

 brane-formation and activation can be induced, we are led to the 

 further inference that this colloidal change affects chiefly if not 

 exclusively the surface-layer (cortical zone or plasma-membrane) 

 of the egg. Thus typical membrane-formation can be induced 

 by brief treatment with pure isotonic solutions of neutral salts.^ 



1 On account of the hysteresis of the gelatine system, the melting temperature 

 is typically several degrees higher than the solidification-temperature; it is also 

 higher after the gel has stood some time than immediately after solidification. Cf. 

 Pauli (Pascheles): Archiv f. d. ges. Physiologie, 1898, Vol. 71, p. 336. 



2 R. S. Lillie: American Journal of Physiology, 1910, Vol. 26, p. 106. The fact 



