138 A. FRANKLIN SHULL AND SONIA LADOFF 



produced, as a result of their metabolic activities, differences 

 between the food cultures that did not exist at first. Thus, 

 it might be expected that Chlamydomonas, a green organism, 

 would carry on photosynthesis, with the resultant liberation of 

 oxygen. It seemed not improbable that oxygen might produce 

 part of the effects in the experiments with Chlamydomonas. 

 This was the more plausible since, as Whitney states, marked 

 effects were produced only when large numbers of Chlamydo- 

 monas were present, and only when the dishes were kept in 

 direct sunlight. Both of the conditions named should result 

 in the production of relatively large quantities of oxygen in 

 solution. 



If it should appear that any or all of these agents present in 

 the Chalmydomonas cultures have any considerable effect in 

 increasing male-production, Whitney's conclusion that his experi- 

 ments gave evidence of an effect of nutrition would lose much 

 of its support. If, on the other hand, these obvious factors 

 could be shown to have no effect whatever, the belief that nutri- 

 tion effected the increase of male-production noted would be 

 greatly strengthened. 



It may be stated in advance that our results may be inter- 

 preted as being largely in support of Whitney's contention; for, 

 while one of the suspected agents (oxygen) gave positive re- 

 sults, its effect was much smaller than that which Whitney 

 reported. Our experiments are the more significant because 

 we have worked with a line of rotifers kindly sent to us by Dr. 

 Whitney in January, 1915, from the line used in his own experi- 

 ments. We can only regret that our experiments were not con- 

 ducted by Dr. Whitney himself, as we have had some difficulty 

 in duplicating his conditions merely from his pubUshed accounts. 



In the account which follows, we separate the experiments 

 aimed to test the effect of dilute bouillon from those designed 

 to test the effect of oxygen. 



