Artificial Parthenogenesis 119 



Another possibility is that the act of fertilization in- 

 creases the permeability of the egg. This idea, which 

 seems attractive, was first suggested and discussed 

 by the writer in I906. 1 He had found that when 

 fertilized and unfertilized eggs were put into ab- 

 normal salt solutions, e. g., pure solutions of NaCl, 

 the fertilized eggs died more rapidly than the unfer- 

 tilized eggs and he pointed out that these experiments 

 suggested the possibility that fertilization increases 

 the permeability of the egg for salts. The reason for 

 his hesitation to accept this interpretation was, that 

 the fertilized egg is also more easily injured by lack 

 of oxygen than the unfertilized egg and in this case 

 the greater sensitiveness of the fertilized egg was ob- 

 viously due to its greater rate of metabolism. Later 

 experiments by the writer showed that the fertilized 

 egg can be made more resistant to abnormal salt solu- 

 tions if its development is suppressed by lack of oxygen 

 or by KCN or by certain narcotics. With our present 

 knowledge it does not seem very probable that lack 

 of oxygen diminishes the permeability of the egg, but 

 we know that it inhibits the developmental processes. 

 Warburg has made it appear very probable that the 

 fertilized egg is impermeable for NaOH and if this is 

 the case it should also be impermeable for NaCl. 2 



1 Loeb, J., Biochem. Ztschr., 1906, ii., 87. 



3 Unless the egg is left so long in the pure NaCl solution that its 

 permeability is increased. 



