Errect 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 
hypertonic solution or for a somewhat longer time to normal 
sea-water in which the oxidations of the egg are suppressed. 
Ss 
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