OXYGEN AND MALE PRODUCTION 473 



EXPERIMENTS SHOWING THAT WATER CONTAINING A SMALL 



AMOUNT OF FREE OXYGEN WILL ABSORB ADDITIONAL 



FREE OXYGEN FROM THE SURROUNDING AIR IN 



DARKNESS 



It is not only important to determine the amount of oxygen 

 generated by Chlamydomonas in the sunlight, but it is also 

 equally important to determine the amount of oxj^gen that is 

 absorbed from the air by the culture water when in darkness. 

 When Chlamydomonas and Polytoma were added to the old 

 stable-tea culture water which contained only a small quantity 

 of free oxygen and then the culture was placed in darkness for 

 several days the quantity of oxygen increased in the culture 

 water several cubic centimeters per liter. This is shown in 

 tables 2, 5, and 7. In the absence of light Chlamydomonas 

 does not carry on photosynthesis and consequently does not give 

 off free oxygen. 



Clear old stable-tea culture was taken, in some experiments it 

 was filtered and in others it was used unfiltered, and the amount 

 of free oxygen determined at the beginning of each experiment. 

 Then several stender dishes containing about 50 cc. of this 

 water was placed in darkness and at successive intervals of 

 twenty-four hours the contents of a dish was tested for free 

 oxygen. Table 2 shows that the culture water graduUay ab- 

 sorbs free oxygen from the air throughout the three to four 

 days' exposure until it usually amounts to from 7 to 8 cc. to a 

 liter. 



EXPERIMENTS SHOWING THAT FEWER MALES IN HYDATINA 

 SENTA ARE PRODUCED IN SUNLIGHT, WHERE PRE- 

 SUMABLY THE AMOUNT OF FREE OXYGEN IS 

 HIGHER, THAN IN DARKNESS WHERE THE 

 AMOUNT OF FREE OXYGEN IS LOWER 



In these experiments large-mouthed bottles about 1^ inches 

 diameter were used. Into each there was put a mixture of 50 

 to 60 cc. of filtered old stable-tea culture water, Chlamydomonas, 

 and a little Polytoma. In the bottles in the sunlight about 1 

 to 1.5 cc. Chlamydomonas were put in order that there might 

 be a large quantity of oxygen generated. In the bottles in 



