MALE-PRODUCTION IN HYDATINA 529 



Oxygen derived from photosynthesis. Euglena was used in these 

 tests. Cultures of a species that formed a sheet of green animals 

 in a somewhat inactive, though not encysted, state along the sides 

 of the aquarium were maintained. A considerable quantity of 

 Euglena was usually available, and it was possible to make nearly 

 as thorough a test as was made with manure scum. Table 4 

 states in tabular form the nature of the tests and their results. 



Test No. 5, of six parts, gives the best idea of the Euglena ex- 

 periments described in this paper. If the results of this test be 

 applied to one of the Euglena-rotifer experiments, presently to be 

 described, they indicate that the water used in the experiment 

 contained 6.05 cc. of oxygen per liter at the outset (a). When 

 Euglena was added as food, the water contained 6.58 cc. of oxygen 

 per liter (b). After four hours in direct sunlight, it contained 

 9.27 cc. per liter (c), but on standing overnight the oxygen content 

 fell to 7.35 cc. per liter (d). 



In the control the water contained 6.05 cc. per liter at the 

 outset (a) ; 5.51 cc. after manure scum was added (e), and 4.63 cc. 

 per liter after the dish had stood twenty hours (f) . 



It should be remarked that probably neither the Euglena nor 

 the manure scum used in test No. 5 was as abundant as in one of 

 the rotifer experiments, though the difference could not have been 

 great. Accepting these results as typical, it appears that the 

 mean oxygen content in one of the Euglena cultures was 



6.58 + 9.27 A /9.27 + 7.35 ,,. 



X4) + ( X 16 , 



' ' ^ '31.70+ 132.96 



20 20 



8.233 cc. per liter while the mean oxygen content of the control 



was 



5.51 + 4.63 



= 5.07 cc. per liter. 



Thus the absolute excess of oxygen in the Euglena dishes 

 over the control was about 3.16 cc. per liter. Relatively the 

 Euglena dishes contained about 62 per cent more oxygen than the 

 manure-scum cultures. As was pointed out above, the quantity 



