NO. 6 EFFECTS OF I.U.IIT ON ALGAE MEIER I3 



flasks, the filters, and the glass bottoms of the water baths were 

 cleaned whenever necessary. While the filters were being cleaned, 

 the culture flasks were kept in a covered dark box. 



The temperature of the baths was regulated by a thermostat set 

 at 21° C. throughout the experiment. The experiment was in progress 

 from February 7 to March 24, 1933. 



A uniform medium and uniform inoculation were insured for all 

 the cultures by the following method: A 3-liter pyrex glass flask 

 was fitted with a rubber stopper through which was inserted a large 

 glass tube. One end of the tube was plunged in the culture medium, 

 the other fitted in rubber tubing with a stopcock ending in a glass 

 pipette. A second smaller glass tube was inserted through the rubber 

 stopi)er, then connected to a compressed air tube by rubber tubes 

 and a glass tube with cotton filters to filter out dust. (See pi. 3, 

 fig. I.) The culture medium Detmer i^, for the 24 individual flasks 

 was made up in this large previously sterilized flask, which was 

 again sterilized in the autoclave at 20 pounds pressure for 20 minutes. 



About 100 cc of a dark green suspension of cells of S'tichococcus 

 bacillaris that had been growing in a north window for one month was 

 used to inoculate the 3-liter flask of Detmer .'t solution. Twenty-four 

 hours later the solution was well shaken and siphoned into each steril- 

 ized 300-cc flask to the previously marked loo-cc level. 



Three extra cultures were placed in the north, south, and west 

 windows of the tower. Samples of the inoculated medium were mea- 

 sured by the nephelometer, the pH was determined colorimetrically, 

 and microscopic counts were made at the time when the flasks were 

 adjusted in the baths and the experiment started. Microscopic counts, 

 nephelometer measurements, and pH determinations were also made 

 at the close of the experimental period. The results of this experi- 

 ment are indicated in tables 2 to 9 and will be discussed in connection 

 with those obtained in the fifth experiment. 



FIFTH EXPERIMENT 



A fifth experiment, a repetition of the fourth experiment with 

 the exception of the duration, was carried on from May 29 to June 

 13, 1933. The results of this experiment are assembled with those 

 of the fourth experiment in tables 2 to 9. 



THE pH OF THE CULTURES 



As Kostychev (1931) points out, the change of pH is a factor not 

 to be ignored when stimulation or retardation of enzyme action, elec- 



