PuHyYsIOLOGIOAL Erreots oF Lack or OxyGen 403 
less preceded that in the normal eggs by three or four min- 
utes. 
The experimental eggs as well as the control eggs were 
fertilized at the same time and in the same dish with a large 
amount of sperm. The process of driving out the oxygen 
by hydrogen was begun some ten or fifteen minutes after 
fertilization. About half an hour later cleavage occurred, 
usually first in the gas-chamber. At this time all the oxygen 
was probably not yet driven out of the eggs, so that we were 
dealing only with a partial lack of oxygen. This partial lack 
of oxygen, therefore, often brought about an acceleration of 
cleavage equal to 6 to 10 per cent. of the time necessary for the 
first cleavage.’ These experiments give one the impression 
that when lack of oxygen has reached a certain stage, a 
transitory increase in the development of energy occurs 
within the egg at first (through the formation of poisonous 
substances?). This increase in the development of energy, 
which, in the case of the respiratory center, is of enormous 
practical importance, therefore seems to appear also in such 
cases where its appearance is entirely unimportant, as in 
cleavage. I will not yet commit myself definitely to the 
statement that in case of a partial lack of oxygen a transi- 
tory acceleration of cleavage occurs; but to trace back 
the purposefulness of organized nature to the general chem- 
ical and physical properties of protoplasm seems to me 
much more promising than the assumption of natural 
selection. 
If we summarize the results of these experiments on the 
effects of lack of oxygen on cleavage, we find that in the 
Fundulus egg, where in the absence of oxygen no dissolution 
of the cell-walls of the cleavage-spheres occurs, cleavage can 
continue for more than ten hours without oxygen; while in 
1T am still inclined to believe that, in spite of all the precautions, the hydrogen 
had a slightly higher temperature than the air when it reached the eggs. [1903] 
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