144 



A. FRANKLIN SHULL AND SONIA LADOFF 



Experime7it 17. Continuous rearing in ^0 per cent oxygen. Two 

 sisters were isolated March 31, 1915, one in spring water, the other 

 in similar water first saturated with an atmosphere composed of 40 

 per cent of oxygen. The former dish was kept in air, the latter under 

 a bell jar in an atmosphere containing 40 per cent of oxygen. From 

 each parent was reared a line under the same conditions as those in 

 which the parent female was placed. In the oxygen line, only the 

 parents and several additional members of each family were kept in 

 oxygenated water. Four or five of the first daughters of each family 

 were kept in oxygenated water, and from among them the parent of 

 the next generation was selected. The remaining daughters in each 

 family were transferred to spring water, where they reached maturity. 

 Whatever effect the oxygen has, therefore, must be exerted in early 

 larval stages, or in the egg, or in the body of the mother. From the 

 previous experiments of Shull ('12) it is to be expected that the egg or 

 oogonial stages are the only ones in which the life cycle can be altered. 



TABLE 14 



Recording two lines derived from sisters, one reared in untreated spring water, the 

 other in water which was first saturated with an atmosphere of which 40 per 

 cent was oxygen, then placed in a corresponding atmosphere. The oxygen line 

 yields more male-producers than the control 



