ORIGINAL METHOD OF ARTIFICIAL PARTHENOGENESIS 169 



which crops up again and again in provoking the development 

 of eggs by hypertonic solutions: it is that the eggs develop only 

 if the supply of oxygen in the hypertonic solution is sufficient. 

 If they lie thickly upon one another, a mutual struggle for 

 oxygen takes place, and the hypertonic solution remains with- 

 out effect. The same happens when the eggs are covered with 

 too deep a layer of water, which prevents a rapid diffusion of 

 oxygen into them. 



5. If unfertilized eggs remain longer in the hypertonic sea- 

 water than is necessary for their development, they will disin- 

 tegrate when put back into normal sea-water. After transfer- 

 ence into normal sea-water they break up into small droplets; 

 they do not undergo such a change while they are in the hyper- 

 tonic solution. This destructive effect of the hypertonic solu- 

 tion can be inhibited by depriving the hypertonic solution of 

 oxygen or by adding a trace of KCN or of chloral hydrate to 

 the sea-water. 1 Fertilized eggs suffer more rapidly in the hy- 

 pertonic solution than unfertilized eggs, and they can also be 

 protected against the toxic action of the hypertonic solution by 

 the suppression of the oxidations in the egg. The reason that 

 fertilized eggs are injured more rapidly by the hypertonic solu- 

 tion than the unfertilized eggs is probably due to the fact 

 that the rate of oxidations is so much greater in the fertilized 

 than in the unfertilized eggs. These facts have already been 

 discussed in a previous chapter. 



Warburg assumes that the oxidations are accelerated ex- 

 cessively by the hypertonic solution. But this is not the case for 

 the fertilized eggs of S. purpuratus on which these experiments 

 were carried out, since Wasteneys and the writer found that the 

 rate of oxidations in the fertilized eggs of S. purpuratus is not 

 accelerated by the hypertonic solution. Either the oxidations 

 are modified by the hypertonic solution so as to lead to the 



1 Loeb, "Ueber die Heimnung der toxischen Wirkung der hypertonischen 

 Losungen aiif das Seeigelei durch Sauerstoffmangel und Cyankalium," Pflilger'a 

 Archiv, CXIII, 487, 1906. 



