534 



A. FRANKLIN SHULL 



Comparison of the second and third divisions of the table indi- 

 cates that oxj^genation of the water increases the proportion of 

 the male-producers by 3.5 per cent. The first and third divisions 

 show that Euglena increases male-production by 9.7 per cent, of 

 which 3.5 per cent is presumably attributable to the oxygen lib- 

 erated in photosynthesis, leaving 6.2 per cent to be caused by 

 some other factor, probably the food itself. The food, if this 

 assumption is correct, is a little less than twice as effective as the 

 oxygen. 



Experiment 4- Euglena versus manure scum, spring water 

 versus manure solution. The effects of the four agents named, in 

 conjunction with one another and in opposition to one another, 

 are here tested. On each of the dates named in table 6 four 

 rotifers were placed in each of four dishes. In two of the dishes 

 was placed manure solution, the food in one of these being Eu- 

 glena, in the other manure scum. Into the other two dishes was 

 put spring water, the food in one of them being Euglena, in the 



TABLE 6 



A comparison of the effects of Euglena and vianare scum, arid of spring ivater and 

 ■manure solution, upon the proportion of male-producers in the rotifer 



Hydatiua senta. 



