116 



DAVID DAY WHITNEY 



TABLE 5 



Experiments with the New Jersey Hydatina senta at a temperature of about 25°C. 

 showing that green food will cause mothers to produce male-producing daughters 

 as readily in darkness without an excess of oxygen as in the sunlight with an 

 excess of oxygen present 



In the mass culture experiments recorded in this paper and 

 in a former one a high percentage of male-producing females were 

 produced when there was an abundance of growing and repro- 

 ducing Chlamydomonas with its accompanying excess of oxygen 

 in the culture water standing in direct sunlight. As the nu- 

 trients of the bouillon or stable tea were being gradually con- 

 sumed the Chlamydomonas gradually ceased reproducing. 

 Some of them went into a quiescent state while others in the 

 adult stage remained more or less motile. When in sunlight 

 during the day they were actively swimming about near the sur- 

 face of the water but at night they also became quiescent until 

 the sunlight of the next day caused them to become active again. 

 During these days when the Chlamydomonas were in these 

 stages just described the rotifers were unable to eat many of 

 them and consequently as they were rather poorly nourished 

 they produced only female-producing females. However, the 

 point to be noted is that during this period there was a formation 

 of gas each day which collected in large bubbles under the scum 



