354 PROTOPLASMIC ACTION AND NERVOUS ACTION 



agents;^ in these eggs an after-treatment with hypertonic 

 sea water is required to complete the activation. Solu- 

 tions of these salts containing CaCla or MgCla are 

 ineffective; pure isotonic solutions of CaCla and MgCla 

 also fail to induce activation; apparently the initial 

 effect of the activating agent must be to increase permea- 

 bility, while the alkali earth salts have the reverse effect. 

 This is probably the reason why when added to the pure 

 alkali salt solution they counteract those effects (activa- 

 tion, stimulation, and toxic action) which are dependent 

 on increase of permeability. 



That the initial effect produced by the pure alkali 

 salt solution is a permeability-increasing one is to be 

 inferred from the general nature of the action of such 

 solutions on living cells. The evidence is more direct 

 in the case of pigmented eggs like those of Arbacia, in 

 which the pigment visibly diffuses into the surrounding 

 pure solution (of Nal, KCNS, etc.) after a few minutes' 

 immersion. In the Ca-containing solution this effect is 

 absent; the permeability-increasing and the activating 

 effects are thus simultaneously prevented. A similar 

 though less complete preventive effect is produced by 

 various anaesthetizing compounds, especially higher 

 alcohols; these when present in the anaesthetiz- 

 ing concentrations (i.e., those which arrest cell- 

 division reversibly) retard or prevent the permeability- 

 increasing and activating action of the pure solu- 

 tions.^ 



Loeb's extensive researches on artificial partheno 

 genesis have shown conclusively that permeabilicy- 



^ Journal of Morphology, XXII (191 1), 695. 

 'Journal of Experimental Zoology, XVI (1914), 591. 



