DAILY RHYTHMS 



495 



The peculiar combination of large transients and little ultimate phase 

 shift (Fig. 10) is explained by the temperature insensitivity of the A 

 component. The fact that some phase shift is ultimately attained is 

 taken to imply a slight feedback of B on ^ that is demonstrable by 

 other types of experiment briefly described below. 



Figure 1 1 summarizes experiments with the Drosophila eclosion 

 rhythm in which the flies are subjected to simultaneous light and 

 temperature periodicities. The phase relations of the light and tempera- 

 ture cycles are systematically varied in the twelve experiments. On 

 hypothesis, the light cycle entrains the A oscillator and the temperature 



Fig. 11. The figure shows the ef- 

 fect on the Drosophila eclosion 

 rhythm of simultaneous periodic 

 cycles of temperature and light. 

 Two successive days are shown 

 for twelve separate cultures. The 

 graphs are arranged so that the 

 phase of the light-dark (shaded) 

 cycles are synchronized, and the 

 phase of the temperature cycle of 

 each culture is displaced 2 hr from 

 the phase of the culture shown just 

 above. The temperature curve is ap- 

 proximately sinusoidal with a mean 

 of 18°C and an amplitude of ±8°C. 



