FOOD AND OXYGEN IN CONTROLLING SEX 



119 



scum was used as food for the rotifers. Shull and Ladoff used 

 similar feeding methods in their experiments and in order to 

 duplicate their work and to test their results the same kind of 

 food as they used has been used in the present experiments. 



In some of the experiments the culture water was first more 

 or less saturated with oxygen by filling a long glass tube with the 

 culture water and connecting this tube to a steel cylinder filled 

 with compressed oxygen and forcing out two-thirds of the culture 

 water and allowing the oxygen to replace that which was forced 

 out. Then the water in the tube was thoroughly shaken in 

 contact with the oxygen. After the shaking was completed the 

 contents of the tube was poured out into a watch glass which 

 was then placed in a Novy anaerobic culture jar. This jar was 

 connected to a vacuum water pump and 40 to 60 per cent of the 

 contained air removed. Immediately after this the jar was dis- 

 connected from the water pump and connected to the cylinder 

 of compressed oxygen and the oxygen was allowed to flow into 

 the jar and to replace the air that had been pumped out. After 



