14 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



of the egg the oxidations in the unfertilized egg are accelerated 

 from four to six times their natural rate. 



This idea is further supported by the fact observed by 

 Wasteneys and the writer that if we cause complete cytolysis 

 of the unfertilized eggs of the sea-urchin by saponin or by 

 distilled water, the rate of oxidation is thereby raised to the 

 same amount as if the eggs were fertilized by sperm, although 

 these eggs are dead. This suggests the idea that the cytolysis 

 of the cortical layer removes an obstacle by which the oxidations 

 become possible. It may be that the cortical layer of the 

 unfertilized egg contains an oxidase which cannot act, or an 

 oxidizable substance which cannot readily undergo oxidation, 

 unless the cortical layer is liquefied (cytolyzed). R. Lillie 

 assumes that the cortical layer of the unfertilized egg prevents 

 the diffusion of CO 2 from the egg and that this C0 2 prevents 

 oxidation. This view meets with the difficulty that C0 2 is a 

 good agency for calling forth the membrane formation in un- 

 fertilized eggs, and we shall see that only such substances can 

 do this as diffuse into the egg. 



9. The earlier biologists had realized that the unfertilized egg 

 dies quickly and that the act of fertilization prevents its death. 

 The question arises: How can the spermatozoon accomplish 

 this act ? The causation of development requires two factors, 

 the one is the membrane-forming factor, the other the corrective 

 factor which in the methods of artificial parthenogenesis is 

 supplied by the hypertonic solution. We may raise the question : 

 Is only one of these factors responsible for the prolongation 

 of the life of the egg, or are both responsible ? At first sight it 

 would seem as if the second factor alone were responsible for 

 this effect, since the membrane formation alone raises the rate 

 of oxidations and also hastens the disintegration of the egg. 

 If, however, the eggs are treated with the hypertonic solution 

 they live and develop. This would make it appear as if the 

 membrane formation alone only hastened the natural death 



