110 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



assumption that, while the oxidations are inhibited, certain 

 other processes, such as hydrolyses, go on in the egg, and that 

 these processes lead to the formation of substances which now 

 allow the egg to develop without disintegrating in this process. 

 But the same result can be obtained more quickly if we modify 

 the process of oxidation or some of its effects by putting the 

 eggs for a short time into a hypertonic solution. 



We have already mentioned that it makes no difference in 

 principle whether the eggs are first caused to form membranes, 

 or whether they are first placed in hypertonic sea-water and 

 the membrane formation is instigated afterward. 1 The only 

 difference between the two procedures consists in the fact that 

 in the latter case the eggs must remain much longer in the hyper- 

 tonic sea-water. 



7. If the egg is treated with hypertonic sea-water before the 

 artificial membrane formation, it has to remain about twice 

 as long in the hypertonic solution as if the order of events is 

 reversed. The unfertilized eggs of S. purpuratus were put into 

 hypertonic sea-water (50 c.c. sea-water +8 c.c. 2J m Ringer) 

 and portions of these eggs were transferred to normal sea-water 

 after 30, 60, 90, 120, 150, and 180 minutes. Ten minutes after 

 they were transferred artificial membrane formation was called 

 forth by butyric acid. The eggs which had been 30 and 60 min- 

 utes in the hypertonic solution all disintegrated in the way 

 characteristic for eggs in which membrane formation has been 

 called forth, but which have not undergone this treatment 

 with hypertonic sea-water. A few of the eggs that had been 

 90 minutes in hypertonic sea-water developed. Practically all 

 of those that had been 150 minutes in the hypertonic sea-water 

 developed. Those eggs which had only undergone the treat- 

 ment with the hypertonic solution without being subsequently 

 treated with butyric acid did not develop into larvae. We 



1 For practical purposes the natural order, membrane formation followed by 

 hypertonic solution, is preferable. 



