120 



Scientific Proceedings (38). 



This observation shows that alkali allows or accelerates the 

 development of the egg through the neutralization of an acid. It 

 is possible that we are dealing here with one of the cases which 

 conform with Stieglitz's theory of catalysis by salt formation. 



75 (485) 



How can the process underlying membrane formation cause 

 the development of the egg? 



By JACQUES LOEB. 



In a series of previous papers it was shown that the process 

 underlying the formation of the fertilization membrane is the essen- 

 tial act in the causation of development. It was further shown 

 that this process is essentially a cytolysis or liquefaction of the 

 superficial (cortical) layer of the cytoplasm of the egg. The ques- 

 tion arose, how can this cytolysis or liquefaction cause the egg to 

 develop. It seemed natural to think first of the possibility that the 

 superficial cytolysis rendered the egg more permeable for substan- 

 ces required for its development. 



The possibility that fertilization might increase the permeability 

 of the egg had been considered by me in 1906 {Biochem. Zeit., 

 1906, ii, 87). I had found that a pure solution of sodium 

 chloride is practically harmless for the unfertilized, but very toxic 

 for the fertilized egg. Since lack of oxygen is likewise harmless 

 for the unfertilized and very harmful for the fertilized egg, I was 

 inclined to ascribe the difference in the toxic effect of sodium 

 chloride to a difference in the velocity of chemical reactions and 

 not to a difference in the permeability of the fertilized and unferti- 

 lized egg. I have recently resumed the investigation of this ques- 

 tion with regard to the action of salts, alkalis and acids. 



(a) The action of salts. — As stated, a pure solution of sodium 

 chloride kills the fertilized egg much more rapidly than the unfer 

 tilized egg. In the preceding notice we have stated the concen- 

 tration of hyroxylions below which the egg of Purpuratus can no 

 longer develop. I find that below this limit a pure sodium 

 chloride solution is much less toxic for the fertilized egg than 

 above that limit. These experiments confirm the view that the 

 difference in the toxic effects of a pure sodium chloride solution on 

 the fertilized and unfertilized egg is due to a difference in the 



