PHYSIOLOGICAL EFFECTS OF LACK OF 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. 1 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 



1 1 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 egys. [ T'OSJ 



