112 Artificial Parthenogenesis 



ishes in certain limits with the concentration of OH 

 ions in the solution. 



It is strange that in the eggs of purpuratus the cor- 

 rective effect can also be brought about by exposing 

 the eggs after the artificial membrane formation for 

 about three hours to normal sea water free from oxygen; 

 or to sea water in which the oxidations have been re- 

 tarded by the addition of KCN. This method is not 

 so reliable as the treatment with hypertonic solution. 



What does the hypertonic solution do to prevent the 

 disintegration of the egg after the artificial membrane 

 formation ? The writer suggested in 1905 that the arti- 

 ficial membrane formation alone starts the develop- 

 ment but leaves the eggs usually in a sickly condition 

 and that the hypertonic solution or the lack of oxygen 

 allows them to recuperate from such a condition. The 

 second factor is, according to this view, merely a cor- 

 rective or curative factor. The following observations 

 will explain the reasons for such an assumption. 



The writer found that if we keep the unfertilized 

 eggs after artificial membrane formation in sea water 

 deprived of oxygen the disintegration of the egg fol- 

 lowing artificial membrane formation is prevented for 

 a day at least. The same result can be obtained by 

 adding ten drops of rb per cent. KCN to 50 c.c. of 

 sea water, and certain narcotics, e. g., chloral hydrate, 

 act in the same way. Wasteneys and the writer found 

 that chloral hydrate (and other narcotics) in the con- 



