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.!. 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. 24 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. 
