532 A, FRANKLIN SHULL 



due to escape of oxygen into the air. Quiet water in contact 

 with ordinary atmosphere will not, as a rule at least, retain as 

 much as 9.27 cc. of oxygen per liter. 



The remaining tests in table 4 (Nos. 6 to 9) are so unlike any 

 of the rotifer experiments that it is unnecessary to explain them 

 further than they are explained in the table. All of them con- 

 tribute, however, to the proof that Euglena under various cir- 

 cumstances markedly increases the oxygen content of the water 

 in which it lives. 



Euglena versus oxygen and other substances as male-producing or 

 male-repressing age?its 



Since the quantity of oxygen produced by Euglena and dis- 

 solved in the water is about the same as that dissolved directly 

 from the atmosphere in the rotifer experiments, the effects of 

 Euglena and of oxygen in increasing male-production may be 

 directly compared. Any excess of male-production in the 

 Euglena experiments over that in the oxygen experiments may 

 therefore be attributed to another factor, probably the food. 



The following experiments were designed to compare the 

 effectiveness of Euglena with that of oxygen among the male- 

 increasing agents, and with manure solution and creatin among 

 the male-repressing agents. 



Experiment 3. Eugle^ia versus oxygen. In each of three 

 dishes was placed the same number of rotifers, the number rang- 

 ing from four to eight on different days. Two of the dishes were 

 filled with spring water; to one of these Euglena was added as 

 food, to the other manure scum. In the third dish was placed 

 water that had first been saturated with an air-oxygen mixture 

 composed of about 40 per cent of oxygen and 60 per cent of nitro- 

 gen. Manure scum was added to the water in the third dish, 

 which was then set under a bell jar in an atmosphere of which 40 

 per cent was oxygen. The chemical composition of the medium 

 in the three dishes at the beginning of the experiment was 

 equalized by adding to the Euglena-fed culture as much manure 

 solution (without scum) as was added to the other two dishes 

 with the scum, and by adding to the manure-scum cultures as 



