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A. FRANKLIN SHULL AND SONIA LADOFF 



had hatched; the young females were removed to spring water, 

 and appear in table 20 as 'younger daughters.' The sex-ratio 

 for the older and younger daughters is given separately to show 

 that the effect of the oxygen is as marked at first as it is later. 

 The proportion of male-producers is approximately doubled 

 by the oxygen. 



Experiment 21. Oxygen counteracting weak manure solution. In this 

 experiment two Unes were bred continuously in weak manure solution. 

 From the first several daughters of each generation one was selected 

 to become the parent of the next generation. One line was reared in 

 a dilute manure solution saturated with a 40 per cent oxygen atmos- 

 phere, the other line in a similar (but not oxygenated) solution. In 

 the former line, only the parents and the first few daughters of each 

 family were kept in the oxygenated solution, the other daughters 

 being transferred to spring water. The method of conducting the 



TABLE 21 



Two lines of rotifers, both reared in dilute manure solution, are here recorded. 

 One line was kept in manure solution saturated with an atmosphere of which 40 

 per cent was oxygen. The oxygen increased the number of male-producers 



DILUTE MANURE SOLUTION, AIR 



DILUTE MANURE SOLUTION, 40 PER CENT OXYGEN 



Remainder of family not recorded. 



