312 STUDIES IN GENERAL PHYSIOLOGY 



tubes. After twenty-four hours a blastoderm was formed in 

 all the eggs contained in the oxygen vacuum. Then, how- 

 ever, development stopped entirely, while it continued, of 

 course, in normal sea-water. Never was the beginning of an 



O O 



embryo formed in such a series of experiments in the oxygen 

 vacuum. Development continued in the oxygen vacuum only 

 to a point which would have been reached in normal sea- 

 water in about fifteen hours. 



An egg that ceased to develop in an oxygen vacuum had 

 not necessarily lost its power of development. When. 

 brought back into normal sea-water, it could continue its 

 development; only it was necessary that the egg had not 

 been left too long in the oxygen vacuum. Eggs which were 

 introduced into the oxygen vacuum immediately after fer- 

 tilization could continue their development after they had 

 lain for four days in such a vacuum at a temperature of 

 22 C. If they remained in the oxygen vacuum longer than 

 this, they lost their power of development for all time. 



In these experiments the eggs were contained in only 2-3 

 c.c. of sea-water. One might think that this circumstance 

 had affected the result, I therefore made control experi- 

 ments in which the eggs were kept in just as little sea- 

 water, but in the presence of an abundance of oxygen. In 

 these experiments the eggs developed in an entirely normal 

 way. 



3. In the second series of experiments the eggs remained 

 in normal sea- water for the first twenty -four hours after fer- 

 tilization, and were then introduced into the oxygen vacuum. 

 At this time a blastoderm, but no embryo, was formed. On 

 the next morning an embryo with optic vesicles had formed 

 in nearly all these eggs. The development of those eggs 

 which remained in the oxygen vacuum then came to a stand- 

 still, however. Development, therefore, again continued in 

 the oxygen vacuum about as far as a fifteen-hour develop- 



