Nature of Formative Stimulation 151 



The ferment theory of the activation of the egg by the sperma- 

 tozoon is also wrong. If it were correct the velocity of develop- 

 ment should be accelerated if not doubled if two spermatozoa 

 enter the egg instead of one; or if fertilization by sperm and 

 artificial parthenogenesis are superposed in the same egg. But 

 this is not the case. In neither case is a shortening of the 

 time which elapses between two successive periods of segmen- 

 tation observed.^ 



The further development will be connected with the ques- 

 tion how can the cytolysis of the cortical layer of the egg lead 

 to its development? I may mention the possibility that the 

 cytolysis of the cortical layer facilitates the diffusion of oxygen 

 or of HO ions (bases) or other substances, necessary for the 

 development, into the egg. 



XII 



Let us summarize our results concerning the activation or 

 formative stimulation of the egg. For the normal development 

 at least two agencies are required: the one is the cytolysis of 

 the thin cortical layer of the egg. Any agency which causes 

 this cytolysis (without causing the cytolysis of the rest of the 

 egg) induces development. The spermatozoon as well as the 

 blood and the tissues contain a substance (lysin) which causes 

 only cytolysis of the cortical layer. The lower fatty acids, 

 from formic to capronic, cause only the cytolysis of the cortical 

 layer. Since most cytolytic agencies cause a cytolysis of the 

 whole egg they can be used only if the eggs are withdrawn 

 from their influence after the cortical layer is destroyed but 

 before the rest of the egg has undergone destruction. 



Cytolysis of the cortical layer leads often but not always to 

 the formation of the membrane of fertilization. 



Since all cytolytic substances are lipoid soluble (or destroy 

 lipoids) it is probable, but not proved, that the formative 



1 Another reason is that the velocity of segmentation is purely determined 

 by the egg, no matter what is the nature of the spermatozoon. 



