ACTION OF THE HYPERTONIC SOLUTION 107 
on the other hand, those experiments are important in 
which the hypertonic solution remains ineffective in the ab- 
sence of oxygen, but regains its powers if oxygen be afterward 
admitted. 
The eggs of S. purpuratus were treated with butyric acid 
in the usual manner, and all formed membranes. These eggs 
were then divided between two flasks containing the same 
hypertonic solution. Through one flask bubbled a stream of 
oxygen, and through the other a stream of hydrogen, by means 
of which it had been previously freed from oxygen. The 
temperature was 14°C. After one hour the eggs were trans- 
ferred to normal sea-water (in contact with air). Practically 
all the eggs which had been in the oxygenated hypertonic sea- 
water developed into larvae, while only a small number of larvae, 
amounting to perhaps one-half of 1 per cent of the eggs, devel- 
oped from those eggs which had been in the hypertonic sea-water 
that was free from, or more strictly poor in, oxygen. The 
remaining eggs disintegrated in the manner characteristic of 
eggs that have undergone artificial membrane formation without 
exposure to hypertonic sea-water. I now wished to convince 
myself that the eggs which go to pieces after exposure to hyper- 
tonic sea-water that is free from or poor in oxygen do develop, 
if they are exposed afterward in the same hypertonic solution 
to the air. To this end not all of the eggs were removed after 
the conclusion of the above experiment from the hypertonic 
solution out of which the oxygen had been driven, but some of 
them were left in this hypertonic solution. This time, however, 
the latter was exposed to the air. At intervals of 14, 26, 36, 
A6, 56, and 116 minutes samples of the eggs were transferred to 
normal sea-water. The result is given in Table X. 
From this experiment we can with certainty draw the 
conclusion that the hypertonic solution in these experiments 
is effective only when it contains a sufficient quantity of free 
oxygen. 
