Nature of Formative Stimulation 147 



and upward are applied the membrane formation is always 

 followed after a short pause by a cytolysis of the whole egg. 



The lysins contained in the blood and the spermatozoon 

 act according to my present experience only upon the cortical 

 layer of the cytoplasm but not on the rest of the egg. We get a 

 membrane formation and development but not a cytolj'sis of 

 the whole egg. 



If we go back to the idea of Butschli that protoplasm has 

 the structure of an emulsion we are led to the view that the 

 emulsion of the cortical layer of the egg differs from that of the 

 rest of the egg. There are certain cytolytic agencies which 

 destroy only the cortical layer; while all general cytolytic 

 agencies destroy the cortical layer as well as the rest of the egg. 



IX 



How can the cytolysis of the cortical layer of the egg lead 

 to a membrane formation? Von Knaffl has expressed the 

 following view on this point: ''Protoplasm is rich in lipoids, 

 it is probably mainly an emulsion of these and of proteins. 

 Every physical and chemical agency which is able to liquefy 

 lipoids calls forth a cytolysis of the egg. The protein of the 

 egg can only swell or be dissolved if the state of the lipoids is 

 altered by chemical or physical means. The mechanism of 

 cytolysis consists in the liquefaction of the lipoids and the 

 subsequent swelling or liquefaction of proteins by absorption 



of water This confirms Loeb's view that membrane 



formation is caused by the liquefaction of lipoids." 



We can accept this with a slight modification which refers 

 to the nature of the emulsion. An emulsion requires not only 

 two substances or phases as von Knaffl assumes but in addition 

 a third substance. The third substance serves the purpose of 

 making the emulsion more durable (Lord Rayleigh's theory). 

 The droplets of the emulsion are surrounded by a thin layer 

 of a substance which lessens the surface tension between the 



