OXYGEN AND MALE FRODUCTION 479 



in the culture water of the lots in the darkness. In others, 

 however, a high per cent of oxygen was found at the end of four 

 days. Several determinations of free oxygen were made in the 

 mornings of cultures similar to the above and a small quantity 

 of free oxygen was always found as in experiments 8 and 9. 

 Thus showing that the excess quantity of free oxygen escapes 

 from the culture water during the night and in the mornings no 

 more is found than would have been found in such culture waters 

 if exposed merely to the air. In the cultures in the sunlight 

 much free oxygen was generated during the first three days, 

 which was very evident by the frothy scum on the surface of 

 the water. During this time the rotifers were subjected for 

 many hours each day to a high per cent of free oxygen. During 

 the night the excess of oxygen gradually escaped, but in the 

 simlight of the following day a new excess of oxygen was 

 generated. 



The rotifers in the sunhght were subjected to perhaps 10 to 15 

 cc. of oxygen per liter for a period each day, while the rotifers 

 in the darkness were never subjected to more than was absorbed 

 by the water from the air, 7 to 8 cc. of oxygen per liter. Bear- 

 ing this in mind, it is of considerable interest to compare the 

 sunlight lots with the darkness lots in individual experiments as 

 in 10, 17, and 20 of table 5 or to compare the average results of 

 the total summary of all the experiments. In all the experi- 

 ments excepting no. 11 the per cent of male-producing females 

 is much lower in sunlight where there is an excess of free oxygen 

 than it is in darkness where there is no more free oxygen than 

 can be absorbed from the air. The results of experiment 11 are 

 not clear, inasmuch as there was brilliant sunlight throughout 

 the four days of the experiment. 



Table 6 shows the light conditions throughout these experi- 

 ments of table 5. 



