INORGANIC SALTS i8i 



tions or other factors, involves variability in the pcrme- 

 abihty of the partition; and as a secondary consequence 

 other conditions depending on that permeabiHty, such 

 as electrical polarization, are afifected. Such a concep- 

 tion implies that changes in the supporting protein 

 structure may also influence permeability; but it 

 regards the normal or physiological variations in this 

 property as dependent chiefly on variations in the state 

 of the most external water-insoluble or lipoid portion of 

 the protoplasmic complex. Such a conception allows 

 for a wide range of variability in the permeability of the 

 membrane. The latter is not to be regarded as a con- 

 tinuous lipoid sheet under one set of conditions, which 

 changes without transition, under other conditions, into 

 a state in which the lipoid becomes the discontinuous 

 and the aqueous phase the continuous phase. A bal- 

 anced state, with fluctuations on either side of a mean, 

 which is regulatively maintained by metabolic processes, 

 is rather the one to be conceived as representing the 

 condition actually existing during life. 



A simple case of salt-antagonism, which I have 

 recently studied in the starfish egg,' appears to throw 

 hght upon the more specifically chemical conditions of 

 these phenomena. The fully mature starfish egg (ca. 

 i6o ju in diameter) is surrounded with a layer of jelly-like 

 substance, of 15 to 20 ju in diameter, consisting of 

 water-swollen material (of undetermined nature) sepa- 

 rated or secreted from the egg-protoplasm. 11iis layer 

 is rendered visible by mounting the eggs on a slide, with 

 cover-glass, in a suspension of India ink, to which the 

 jelly is impermeable; it then appears under the niicro- 



'Jour. Gen. Physiol., Ill (1921), 783- 



