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 
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- 
Digitized by Microsoft® 
