474 



DAVID D. WHITNEY 



darkness not as much Chlamydomonas could be added because 

 much of it would die, probably from lack of oxygen, decompose 

 and befoul the water so as to prevent the normal growth and 

 reproduction of the rotifers. In these experiments ten adult 

 rotifers were put into each bottle of culture water and food and 

 one bottle was placed in a pan of running water in the sunlight 

 and the other bottle was placed in darkness at room temperature. 

 Both of these bottles were left undisturbed for six days, then 

 each was well stirred and a few drops of the liquid immediately 

 taken out and the sex of the rotifers in these drops were recorded. 

 In table 3 it is seen that in the sunlight the males constituted 

 8 + per cent of the rotifer population of 1736 individuals, while 

 in the darkness the males constituted 28 + per cent of the 

 population of 1654 individuals. 



TABLE 3 



Showivg that rotifers kept in darkness where there is no production of free oxygen 



by the Chlamydomonas produce more males than rotifers do which are kept 



in the sunlight in the midst of considerable quantities of free 



oxygen that is given off by the Chlamydomonas 



