130 



DAVID DAY WHITNEY 



TABLE 9 



Bacterial counts in cultures made from tap water and vigorous growing Polytoma 

 cultures, reared in one part stock stable tea and three parts tap water, showing a 

 great decrease in the number of living bacteria during an interval of forty-eight 

 hours under ordinary laboratory air conditions 



GENERAL DISCUSSION 



It has been shown in a former paper together with the present 

 one that in nine different species of rotifers the production of 

 male-producing daughters can be controlled by the food condi- 

 tions. In all of the nine species the production of male-producing 

 daughters can be brought about by feeding the mothers a 

 sufficient quantity of certain green microorganisms in the 

 sunlight. 



Shull and Ladoff suggest and contend that the oxygen given 

 off by these green microorganisms during photosynthesis in the 

 sunlight is an important factor in causing the mothers to produce 

 male-producing daughters. 



Several years ago it was noted that in 2-4 liter battery jars of 

 newly made stable tea cultures of miscellaneous colorless micro- 

 organisms and Hydatina senta there was an abundance of male- 



