524 



A. FRANKLIN SHULL 



TABLE 1 



Showing the effect of saturation of the water with an air-oxygen mixture, of which 

 60 per cent was oxygen, upon the ratio of maleproducers (c? 9 ) 'o female- 

 producers (9 9 ) 2n the rotifer Hydatina senta 



The method of carrying out the tests was precisely the same 

 as described for experiment 1, except that in the 40 per cent 

 oxygen tests the mixture used in saturating the water and the 

 mixture under the bell jar were made up of three parts air and 

 one part oxygen, instead of equal parts of the two as in the 60 

 per cent oxygen mixture. 



Table 2 shows the results of the experiment. In both of the 

 tests the oxygen mixture produced more male-producers than 

 the control. If the absolute difference between experiment and 

 control be taken as the measure of effectiveness of oxygen, the 

 60 per cent mixture appears to be a little more potent than the 

 40 per cent. If the ratio of male-production in the experiment 

 to male-production in the control is the proper measure of effec- 

 tiveness, then 40 per cent oxygen produced greater results than 

 60 per cent oxygen. In other experiments the impression has 

 been gained that the relative difference between experiment and 

 control is a better measure of the effect produced than is the 

 absolute difference. In this experiment the ratio of the per- 

 centage of male-production in oxygen to the percentage of male- 

 production in the control is 1.51 in the case of the 40 per cent 

 oxygen, 1.41 in the case of the 60 per cent oxygen. The fourteen 

 tests made are too few to use statistically to determine whether 



