ACTION OF THE HYPERTONIC SOLUTION 111 



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. 



