470 DAVID D. WHITNEY 



cavity, thus causing death, while in others the Chlamydomo- 

 nas would form a dense and compact mass in their stomachs 

 which also caused death. By mixing a small proportion of 

 Polytoma with the Chlamydomonas, both of these troubles were 

 avoided. The Chlamydomonas was raised in large quantities in 

 bouillon solution in direct sunlight and the Polytoma was raised 

 in stable tea in darkness. The details of rearing both of these 

 flagellates have been published in former papers. 



In many of the experiments the amount of food was measured 

 in a graduated pipette. The Chlamydomonas and the Polytoma 

 were each separately centrifuged and all of the original culture 

 water drained off. Then just enough old stable-tea culture 

 water was added to allow the Chalmydomonas and Polytoma to 

 be drawn up into the pipette. In this way the amount of food 

 could be quite accurately measured and regulated at will in 

 each experiment. 



It was found that the Chlamydomonas could be transferred 

 from the sunlight to absolute darkness and would remain alive 

 and active for several days, the duration of activity being 

 somewhat dependent upon temperature. 



The amount of oxygen, number of cubic centimeters per 

 liter, whenever determined in the experiments was determined 

 by the Winkler method described in Standard Methods of Water 

 Analysis published by the American Public Health Association 

 of Boston. The sodium thiosulphate solution was standardized 

 against potassium dichromate about three times per week. 



The following experiments are not arranged chronologically, 

 but are so arranged as to present the evidence and data in a 

 logical manner. 



EXPERIMENTS SHOWING THE PRODUCTION OF OXYGEN BY 

 CHLAMYDOMONAS IN DIRECT SUNLIGHT 



It was considered desirable to determine how much free oxy- 

 gen is given off by Chlamydomonas when the culture is in 

 the direct sunlight for several hours. Varying quantities of 

 Chlamydomonas were put into about 50 cc. of old stable-tea 

 culture water and poured into stender dishes, 1 inch in diameter. 



