544 A. FRANKLIN SHULL 



atmosphere, contained on the average about 60 per cent more 

 dissolved oxygen than did the untreated controls. 



Cultures in which Euglena was used for food were also com- 

 pared, relative to their oxygen content, with cultures in which 

 manure scum was used as food. The Euglena cultures under 

 the conditions of the experiments, contained on the average about 

 62 per cent more oxygen than the manure scum cultures. Pre- 

 sumably, therefore, when Euglena increases male-production in 

 Hydatina, as much of that increase is due to oxygen as is directly 

 produced by saturation with a 40 per cent oxygen atmosphere. 



In experiments with Euglena as food, after deducting the in- 

 crease in male-production presumably due to oxygen liberated, 

 it was found that Euglena was two or three times as effective as 

 the oxygen, and in one case many times as effective. The experi- 

 ment in which Euglena appeared to be many times as effective 

 as its liberated oxygen was performed upon a different line from 

 that of the other experiments. This line was tested to discover 

 whether it was responsive to oxygen in another way (laying 

 eggs at surface film or bottom of dish). While it was plainly 

 responsive to oxygen, there is some doubt whether it was as 

 responsive as the other line used. 



Euglena as a male-producing agent was compared with manure 

 solution as a male-repressing agent. The repressing effect of 

 manure solution was a little more than offset by the Euglena 

 (including the effect of the oxygen hberated by the Euglena). 



BIBLIOGRAPHY 



Shull, a. F. 1915 a Inheritance in Hydatina senta. II. Characters of the 



females and their parthenogenetic eggs. Jour. Exp. Zool., vol. 18, no. 



1, January, pp. 145-186. 



1915 b Periodicity of male-production in Hydatina senta. Biol. 



Bull., vol. 28, no. 4, April, pp. 187-197. 



1918 Effect of environment upon inherited characters in Hydatina 



senta. Biol. Bull., vol. 34, no. 6, June, pp. 335-350. 

 Shull, A. F. and Ladoff, Sonia 1916 Factors affecting male-production in 



Hydatina. Jour. Exp. Zool., vol. 21, no. 1, July 5, pp. 127-161. 

 Whitney, D. D. 1914 The influence of food in controlling sex in Hydatina 



senta. Jour. Exp. Zool., vol. 17, no. 4, November, pp. 545-558. 



1917 The relative influence of fgod and oxygen in controlling sex in 



rotifers. Jour. Exp. Zool., vol. 24, no. 1, October, pp. 101-145. 



