RALPH S. LILLIE. 



of acids and bases, as well as under the influence of high temper- 

 atures, is a phenomenon of general occurrence, and its conditions 

 resemble closely those already described as determining the rate 

 and character of activation in starfish eggs. Both processes 

 require time, and end in structural alterations of a definite kind; 

 in the egg membrane-formation is the first visible change, which 

 may be followed by development; in cytolysis the essential effect 

 appears to be an alteration of the surface-layer or plasma-mem- 

 brane of the cell ; this structure loses its normal insulating or semi- 

 permeable properties, with the result that the diffusible cell- 

 constituents pass into solution in the surrounding medium; the 

 cell then disintegrates. The physico-chemical conditions of 

 cytolysis have been investigated most completely in red blood- 

 corpuscles, and exact data are available with reference to the 

 influence of both the concentration of the haemolytic agent and of 

 temperature upon the rate of haemolytic. action. Many facts 

 indicate that a change similar in kind to that underlying cytolysis, 

 only reversible and of brief duration, forms a primary feature of 

 both normal and artificial activation. According to Loeb an 

 incipient or superficial cytolysis is the first stage in the chemical 

 activation of sea-urchin eggs; 1 and this view has been substanti- 

 ated by a large number of investigations, which have shown that 

 cytolytic agents of the most varied kind, chemical and physical, 

 may cause parthenogenesis. 



All of this evidence indicates that the initial change in the 

 activation of the resting egg is superficial, and associated with a 

 general increase in the permeability of the egg-surface to water- 

 soluble substances and water. 2 One general consequence of 

 such a change is electrical depolarization; and from the analogy 

 with the phenomena of stimulation it seems probable that this 

 electrical variation, as such, forms the critical change of condition 

 by which the course of the metabolic processes in the egg is so 

 modified as to initiate development. Structural and metabolic 

 alterations go hand in hand and mutually influence each other, 

 as has lately been especially emphasized by Child; 3 and the ini- 



1 J. Loeb. "Artificial Parthenogenesis and Fertilization," Chapter 17. 



2 Cf. my recent paper in Amer. Journ. Physiol., 1916, Vol. 40, p. 249. 



3 C. M. Child, " The Regulatory Processes in Organisms," Journal of Morphology, 

 1911, Vol. 22, p. 173; cf. also "Senescence and Rejuvenescence," LJniversity of 

 Chicago Press, 1915, especially Chapters i and 2. 



