378 



D WIGHT E. MINNICH 



mal was subjected to a second set of trials of the same aggregate 

 duration as the first, but in the other of the two light intensities. 

 The order in which the two intensities of illumination were em- 

 ployed was varied from time to time. Sometimes the first de- 

 termination was made in the more intense Ught; the second, in the 

 less intense. Sometimes the reverse order was observed. 



A single series of records in one intensity of non-directive light 

 together with the corresponding series in the other intensity con- 

 stitute what I shall term a pair of determinations. The protocol 

 of such a pair of determinations on bee no. 42 is given in table 3. 

 JFour or five pairs of determinations were usually made on each in- 

 dividual of an experiment in the course of a day, beginning 



TABLE 3 



between 8 and 9 o'clock in the morning and concluding between 4 

 and 5 in the afternoon. The bees often seemed to become slug- 

 gish in the late afternoon. Whether this was due to fatigue or a 

 natural rhythm of activity from day to night, I am unable to say. 

 This phenomenon, however, led me to abandon any attempt to 

 continue experimentation much after 5 o'clock. 



On the third and concluding day of the experiment, the scheme 

 of the second day was again carried out as far as possible. Bees 

 usually survived the first two days of experimentation, and in 

 case they did not, the data on them were discarded. A number 

 of individuals, however, failed to survive in fit condition for the 

 trials of the third day, and still others had to be discarded in the 

 course of the day, although in both cases the results were counted. 



