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zooglea of miscellaneous bacteria the species of predominating 

 bacteria may vary with the age of the zooglea. This is indicated 

 in experiment 5 in which all the rotifers died rather quickly, 

 presumably from some toxic poisoning produced by the bacteria 

 in this older scum. The fourth point determined is that no one 

 can say in advance how well the rotifers in such irregular cultures 

 are going to thrive. As no two watch glass cultures can be 

 made identical in regard to their food contents in species or in 

 number of bacteria there can be expected no uniformity of their 

 effects upon the rotifers in producing male or female-producing 

 daughters. This is amply illustrated by the experiments in 

 table 8 and also in many of the experiments of Shull and Ladoff. 

 The fifth point demonstrated is that male-producing females of 

 the New Jersey strain of Hydatina senta are produced equally 

 well under ordinary air conditions as under a 40 to 60 per cent 

 excess of oxygen. 



