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, 

 46, 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. 



