612 RALPH S. LILLIE 



It is of course also possible that the actual entrance of the salt 

 into the egg is unnecessary, and that a purely superficial action 

 sufficient to increase permeability to a critical degree and thus 

 cause a definite depolarization-effect is all that is necessary. 

 There is at present no certain means of deciding between these 

 two alternatives. If the salt increases permeability to a suffi- 

 cient degree, it will naturally enter the egg and produce certain 

 effects in its interior. It is, however, clear that there is nothing 

 specific about the salt-action; all that is needed is that it should 

 be sufficiently energetic. The entrance of special substances 

 from outside into the egg is not necessary for parthengenesis : 

 the effects of temporary warming and mechanical agitation upon 

 starfish eggs are a sufficient proof of this. On the other hand, 

 certain substances as fatty acids and lipoid-solulle alkahs, do 

 undoubtedly produce their effects by penetrating the egg.^^ 

 The comparative ineffectiveness of the lipoid-insoluble and non- 

 penetrating alkalis and acids indicates this clearly. The most 

 probable conclusion seems to be that the same effect can be 

 produced by a purely superficial action, like that of a salt or the 

 electric current, as by one operating at some region within the 

 interior of the egg. 



There are many indications that the primary effect in the acti- 

 vation of the egg — whether by the spermatozoon or a partheno- 

 genetic agent — is superficial and consists in an alteration of the 

 surface-layer of protoplasm — the region somewhat vaguely 

 designated as plasma-membrane. The term 'plasma-membrane' 

 in its application to the surface-film seems at present to require 

 more precise definition. The conception of this structure as a 

 thin homogeneous haptogen membrane exercising passive me- 

 chanical and osmotic functions is clearly inadequate. It must 

 rather be regarded as essentially a superficial portion of the living 

 protoplasm, characteristically modified in its composition and 

 physical properties by surface forces. We must thus ascribe to 

 it a characteristic chemical organization and metabofism as 

 well as the characteristic physical and other properties, such as 



1^ Cf. Loeb's recent paper on "The comparative efficiency of weak and strong 

 bases in artificial parthenogenesis," Jour. Exp. Zo5l., 1912, vol. 13, p. 577. 



