OXYGEN AND MALE PRODUCTION 485 



EXPERIMENTS SHOWING THAT THE FREE OXYGEN CONTENT 

 OF WATER IS NOT INCREASED WHEN CHLAMYDOMONAS 



IS ADDED 



After the preceding experiments had been completed, it was 

 reahzed that perhaps there was a sufficient amount of free oxy- 

 gen retained within the individual cells themselves of Chlamy- 

 domonas to exert an appreciable influence when the Chlamydo- 

 monas were transferred to other culture waters. In order to 

 test this possibility, the experiments recorded in table 8 were 

 performed. 



The Chlamydomonas was allowed to remain in the sunUght 

 for several hours; then it was centrifuged, its culture water 

 drained off, sufficient quantity of water added to liquefy it, and 

 definite quantities of it added to various kinds of water. The 

 water used was mainly rain-water, which varied widely in the 

 free oxygen content. The rain-water that had been standing in 

 the pipes from a large storage tank contained less than 1 cc. of 

 free oxygen per liter, while rain-water in battery jars which had 

 been exposed to the air for several days contained as much as 7 

 or 8 cc. of free oxygen per liter. Chlamydomonas was added to 

 these two kinds of rain-water. Oxygen tests were made im- 

 mediately with some unfiltered lots containing Chlamydomonas, 

 while other lots were first filtered before being tested. In a few 

 experiments Chlamydomonas was allowed to remain in the water 

 about ten minutes, while in others it was allowed to remain 

 about four hours before the tests were made. 



It was found that a considerable error was introduced by 

 filtration. The quantity of oxygen was increased even in the 

 most hurried filtration and was increased very markedly if the 

 filtering process was prolonged for a few minutes, especially in 

 the water that contained a very small quantity of free oxygen 

 at the beginning of the experiment. In some experiments the 

 water was decanted before testing for oxygen, but this method 

 was only feasible when a sufficient time had elapsed to allow the 

 Chlamydomonas to settle to the bottom of the bottle. 



In none of these experiments, when the error due to filtration 

 was taken into consideration, was there found any evidence to 



