120 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
Hence by a treatment with a hypertonic solution for a 
sufficient length of time unfertilized eggs retain as long as they 
live the quality of being immune against the disintegration 
which follows artificial membrane formation. What is the 
nature of this alteration? Warburg found that in unfertilized 
eggs without membranes the rate of oxidation is increased by 
hypertonic solutions, and we were able to confirm his observa- 
tion. This suggested the idea that possibly a treatment of such 
eggs with a hypertonic solution would raise their rate of oxida- 
tion permanently and that this might be the cause of their 
immunity against the disintegrating processes following arti- 
ficial membrane formation. This was a priori not very probable 
since we found that the corrective effect of the hypertonic solu- 
tion after artificial membrane formation in the egg of S. pur- 
puratus is not due to an increase in the rate of oxidations. 
6. We were therefore anxious to see if the rate of oxidation 
caused by the treatment of unfertilized eggs of S. purpuratus 
(without membrane formation) was permanently maintained. 
For this purpose the consumption of oxygen in an unfertilized 
lot of eggs of S. purpuratus was measured at 18° C. in four suc- 
cessive periods. 
Oxygen 
Consumption 
in 90 Minutes 
In normal sea-water =. 20... 5 30)4,.%hs cael as Se 0.30 mgm. 
In hypertonic sea-water (50 c¢.c. sea-water+9c.c. 23 m 
NaCl-EKEl4-CaCl) . os net thos tae Re ee 0.67 mgm. 
In normal sea-water half an hour later................. 0.51 mgm. 
In normal sea-water twenty-one hours later............. 0.48 mgm. 
While it is obvious that these eggs continue to show an 
increased rate of oxidation for at least 22 hours, the rate is 
very much lower than after fertilization or after the artificial 
membrane formation. Through the treatment of the eggs in 
the above-mentioned experiment the rate was increased 2.2 
times and the next day it had fallen to 1.6 times. This 
