INORGANIC SALTS i8i 



tions or other factors, involves variability in the perme- 

 ability of the partition; and as a secondary consequence 

 other conditions depending on that permeability, such 

 as electrical polarization, are affected. 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 

 light upon the more specifically chemical conditions of 

 these phenomena. The fully mature starfish egg (ca. 

 1 60 /x in diameter) is surrounded with a layer of jelly-like 

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

 water-swollen material (of undetermined nature) sepa- 

 rated or secreted from the egg-protoplasm. This 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 micro- 



^ Jour. Gen. Physiol., Ill (1921), 783. 



