OXYGEN AND MALE PRODUCTION 491 



male-producing females. Furthermore, if the total averages are 

 compared, it is seen that the high percentages of male-producing 

 females are identical, although the quantity of free oxygen at 

 the end of the three-day period averages in lots A at 5-1- cc. 

 per liter and in lots B at 3 -f cc. per liter. Thus demonstrating 

 that the production of male-producing females does not depend 

 directly upon the presence of appreciable quantities of free 

 oxygen in the culture water. 



SUMMARY 



1. In the sunlight free oxygen in considerable quantities is 

 given off by the green flagellates, Chlamydomonas. 



2. In darkness no free oxygen is given off by the Chlamy- 

 domonas. 



3. No appreciable quantity of free oxygen was found to be 

 contained within the individual cells of Chlamydpmonas when 

 they were transferred from their original culture water into 

 other water. 



4. Culture water free from decomposing materials absorbs 

 free oxygen from the surrounding air until its capacity of from 7 

 to 8 cc. per liter is attained. 



5. In the sunlight fewer male rotifers and also fewer male- 

 producing female rotifers are produced in culture water contain- 

 ing Chlamydomonas which have given off much free oxygen 

 than are produced in darkness in culture water containing less 

 free oxygen. This is due to the fact that in the sunlight the 

 Chlamydomonas become less available as food for the rotifers, 

 while in darkness they remain more available for food through- 

 out several days and nights. 



6. Culture water containing the minimum quantity (in some 

 cases less than the minimum quantity) of free oxygen, 1 cc. to 3 

 cc. per liter, in order to allow the normal activities of the 

 rotifers, yields as many male-producing females as culture water 

 containing from 2 to 8 cc. of oxygen per liter. 



7. The general conclusion is that oxygen is a factor in causing 

 a production of males except inasmuch as it is necessary for all 

 life processes and activities of the rotifers. 



