DAILY RHYTHMS 



487 



12 



wo 



Fig. 5. The transient approach to a new 

 steady state is illustrated for two of the 

 Drosophila "Resets" shown in Fig. 4. The 

 eclosion peaks on successive days are 

 plotted underneath each other to illustrate 

 the nature of the transients. The shaded 

 area represents light; at all other times the 

 cultures are in complete darkness. The 

 first arrow corresponds to "dawn" (hour 

 zero) of the previous light-dark cycle. 

 The second arrow corresponds to the be- 

 ginning of the resetting signal. The tran- 

 sients are lengthening ones for culture 8 

 (signal begins 8 hr after dawn), and 

 shortening ones for culture 18. Compare 

 with Fig. 9. 



8 tl 



j 

 I 



I 



I 



14, and 15 (Fig. 4) there are small "subsidiary" peaks at lines D2 and 

 Da, which probably represent a fraction of the fly population in which 

 no phase reset was accomplished. 



Two previous papers from this laboratory (Pittendrigh and Bruce, 

 1957; and Pittendrigh, 1958) have discussed these data in a different 



