264 DAVID DAY WHITNEY 



The colorless Polytoma was reared in stable tea (horse manure) 

 solution in a subdued light while the green Chlamydomonas 

 was reared in bouillon solution in direct sunlight. It is very 

 probable that their values as foods would be considerably dif- 

 ferent, in as much as Polytoma lacks chlorophyl and con- 

 sequently cannot carry on photosynthesis while Chlamydomonas 

 possesses chlorophyl and manufactures and stores starch in 

 its cell. Thus the colorless flagellate would contain neither 

 starch nor sugars while the green flagellate might have more or 

 less of each. 



In order to get new data on these two problems the former 

 experiments upon Hydatina senta were carefully reviewed and 

 new expermients carried out upon the following rotifers: from 

 the order of Ploima the species, Branchionus pala, Diaschiza 

 sterea, Diglena catellina, and from the order of Scirtopoda the 

 species Pedalion mirum. These species were identified by 

 Harry K. Harring, Custodian of the Rotatoria in the United 

 States National Museum, to whom 1 am greatly indebted for 

 the favor. 



Hydatina senta 



The results obtained from numerous experiments carried out 

 upon this species from New Jersey and from England have 

 already been published in detail and need not be repeated again. 

 However, as no diagrams have been published of the American 

 form, diagrams have been drawn to the same scale of a female 

 and a male individual, a parthenogenetic female-producing egg, 

 a parthenogenetic male-producing egg, and of a fertilized egg. 

 These are shown in figure 1. A general review of the results 

 of the former experiments have been put into a plotting in dia- 

 gram 1, showing that a continuous diet of Polytoma caused onh' 

 female-producing females to be produced for nearly two years 

 but when the food was suddenly changed to the green Chlamy- 

 domonas a high percentage of male-producing females appeared 

 within a few days. An important feature of these experiments, 

 which does not show in the diagram, is the place where the 

 stimulus is effective in changing the females from female-pro- 



