Prevention of Death by Fertilization 163 



membrane formation the further entrance of the spermatozoon 

 into the egg is prevented, since the fertilization membrane is 

 impermeable to sperm. This membrane formation leads to an 

 increase in the rate of oxidations and the beginning of the de- 

 velopment of the egg. The latter, however, contains a t(jxic 

 substance, or a faulty complex of conditions which has to be 

 abolished, before the oxidations necessary for development can 

 take place without the egg being destroyed by them. The 

 spermatozoon carries a second substance into the egg which 

 renders it immune against the fatal actions of the oxidations. 

 While the membrane-forming substance of the spermatozoon 

 may be situated at its surface, or superficially at least, the 

 second substance which transforms the egg from an anaerobe 

 into an aerobe must be situated in the interior of the sperma- 

 tozoon; since it can only act if the spermatozoon penetrates 

 into the egg. We see in these observations, concerning the 

 fertilization of the sea-urchin egg by the star-fish sperm, a 

 proof that the activation of the egg by the spermatozoon is 

 also caused by two different substances, one of which causes 

 the membrane formation, while the second renders the egg 

 immune against the toxic action of the oxidations. These 

 data support the assumption made above that the life-saving 

 action of the spermatozoon is due to the fact that it carries a 

 substance into the egg which renders the latter immune against 

 the toxic action of oxidations. 



Ill 

 Seven years ago I found that a number of agencies destroy 

 the fertilized egg much more rapidly than the unfertilized egg. 

 Thus, for instance, while in a pure sodium chloride solution the 

 unfertilized egg of the Californian sea-urchin may be kept alive 

 for several days, the fertilized egg is destroyed in such a solu- 

 tion in less than twenty-four hours. If we use slightly alka- 

 line solutions of sodium chloride the greater resistance of the 



