ACTIVATION OF UNFERTILIZED STARFISH EGGS. 297 



whose action is certainly superficial, as well as by substances like 

 fatty acids, weak bases, and lipoid-solvents, which readily 

 penetrate the plasma-membrane. Those neutral salts of sodium 

 and potassium which are the most effective in inducing m.em- 

 brane-formation, iodides and thiocyanates, are also the most 

 effective in lowering the melting points of protein gels and in 

 promoting water-absorption by such gels.^ Such facts suggest 

 that the salts act in a way similar to that of high temperatures, 

 i. e., by furthering degelation of surface-structures or absorption 

 of water in the surface-layer of the egg. The effect of such an 

 increase in water-content would be to increase the general 

 permeability of this region, since according to the experiments 

 of Bechhold, Ruhland, and others^ the permeability of gels to 

 diffusing substances, especially to colloids, is a direct function of 

 their water-content. 



High temperature, according to this interpretation, acts like 

 other parthenogenetic agents, by increasing the permeability of 

 the surface-layer, — this effect resulting directly from some change 

 in the nature of a degelation or decrease in the viscosity of the 

 colloidal system in this region. Apparently the immediate 

 effect of this change is to allow a chemical interaction to*take 

 place between substances which in the normal resting state of the 

 surface-layer are kept apart. The general fact that identical 

 physiological effects may be produced by lipoid-solvents, and 

 by substances which appear to alter the membrane by interacting 

 chemically with its constituents,^ indicates that the integrity 

 of the plasma-membrane as a semi-permeable partition is the 

 essential factor in preserving the resting condition of the egg.^ 



that this action can be prevented by anesthetics confirms the view that it depends 

 on an increase in the permeability of the plasma-membrane: cf. my recent paper in 

 the Journal of Experimental Zoology, 1914, Vol. 16, p. 591. 



1 Cf. Pauli (Pascheles) : Archivf. d. ges. Physiologie, 1898, Vol. 71. P- 333; Levites: 

 loc. cit.\ Pauli and Rona, Beilrdge zur chemischen Physiologie 11. Pathologie, 1902, 

 Vol. 2, p. 4. 



2 Bechhold u. Ziegler, Zeitschr.f. physik. Chem., 1906, Vol. 56, p. 105; also, "die 

 Kolloide in Biologie u. Medizin," 1912, p. 48. Ruhland: Biochemische Zeitschrift, 

 1913, Vol. 54, p. 59; Freundlich, Kapillarchemie, pp. 515 seq. 



3 When membrane-forming substances act by combining chemically with egg- 

 constituents, it is to be expected that the rate of action will vary with temperature 

 in accordance with the chemical temperature-coefficient. Cf. the experiments of 

 Loeb and Hagedoorn, "Artificial Parthenogenesis and Fertilization," page 146. 



" Cf. my paper, Amer. Journ. Physiol., 191 1, Vol. 27, p. 289. 



