ORIGINAL Metuop oF ARTIFICIAL PARTHENOGENESIS 167 
In this case the NaOH had little effect and hence the 
hypertonicity caused a noticeable increase in the rate since it 
probably increased the number of eggs in which the process of 
membrane formation was started. 
TABLE XXXV 
Coefficient 
Unfertilized Eggs (without Membrane Oxygen 
Formation) in Consumed Gone 
| 
mgm. 
Normal BAN BUEL creche eae Riot afc paral atciays aes mcrae o 0.41 1.00 
50 c.c. hypertonic sea-water+1 c.c. N/10 NaOH| 0.81 2.00 
50 ¢.c. normal sea-water+1 ¢.c. N/10 NaOH .... 0.46 1.20 
4. It is necessary for the developmental effect that the 
hypertonic solution contain free oxygen. if the oxygen is 
driven out of a hypertonic solution sufficiently thoroughly, 
this solution can no longer cause the unfertilized eggs of the 
sea-urchin to develop. The following experiment on the eggs 
of S. purpuratus will serve as an example. The air was driven 
out of a series of flasks each of which contained 50 c.c. 
of sea-water+8 c.c. 23 m NaCl,! by passing chemically 
pure hydrogen through them for several hours, and then 
a pipette full of sea-urchin eggs was introduced into each 
of them. This was effected with the aid of an assistant and in 
such a way that the stopper of the flask was lifted to one side 
over the rim for only one or two seconds and during this time 
the pipette that had been held in readiness was emptied into 
the flask. The current of hydrogen was not interrupted and 
proceeded throughout the whole experiment. Some of the eggs 
were placed as a control in 50 c.c. of sea-water+8 c.c. of 25 m 
NaCl which remained in contact with air. After 128 and 180 
minutes samples of the eggs were replaced in normal sea-water. 
The control eggs which had been in the oxygenated sea-water 
and were transferred to normal sea-water after 128 minutes 
developed practically all into larvae; of the eggs transferred to 
1 This hypertonic solution was slightly alkaline. 
