Effect of Artificial Membrane Formation 83 



seems to be able to segment without disintegrating in the 

 process. While the eggs are without oxygen or in the cyanide 

 solution changes occur in the eggs which allow them to undergo 

 cell division in a normal way, when put back into normal sea- 

 water. While this method is theoretically of interest, the 

 method of treating the eggs with hypertonic sea-water after 

 the membrane formation is for practical purposes preferable, 

 since it is absolutely reliable. 



The experiments thus far reported show therefore that the 

 artificial membrane formation starts the development of the 

 sea-urchin egg, but that it leaves the egg in a sickly condition 

 which causes it to disintegrate rapidly at room temperature. 

 In order to make such eggs normal, they must undergo a second 

 treatment: they must either be exposed for a short time to a j 

 hypertonic solution or for a somewhat longer time to normal | 

 sea-water in which the oxidations of the egg are suppressed. 



