ACTION OF THE HYPERTONIC SOLUTION eh: 
have already stated that the treatment of unfertilized eggs of 
S. purpuratus with hypertonic sea-water alone leads to the 
formation of larvae, not with the eggs of all females, but with 
only a small percentage. 
When the order of events was reversed and the treatment 
with hypertonic sea-water followed the artificial membrane 
formation all the eggs developed if they remained in the sea- 
water from about 50 to 60 minutes. The reason for this differ- 
ence is easily understood if we compare the rate of oxidations 
before and after membrane formation. After membrane forma- 
tion the rate of oxidations is more than four times as large in the 
egg as before (chap. xii). With this fast rate of oxidation the 
eggs need remain only a short time in the hypertonic solution. 
If, however, we put the eggs in the hypertonic solution before 
the membrane is formed, they have to stay more than twice as 
long in the hypertonic solution because the rate of oxidations 
is at first so much slower. 
