574 



PHOTOPERIODISM IN INVERTEBRATES 



is essentially temperature-independent (Hastings and Sweeney, 1957b; 

 Sweeney and Hastings, 1958). Table I summarizes our data with re- 

 spect to this question. It is of interest to find some temperature depend- 

 ence, even though it is not great. The unusual temperature coefficient 

 (period is longer at higher temperatures) suggests that the clock has 

 a temperature compensation mechanism which, however, is not pre- 



Table I. Effect of Temperature and Light Intensity upon Natural Period of 



Gonyaulax Rhythms" 



" The table gives all the data thus far obtained in our laboratories with reference to the 

 natural period in Gonyaulax. Many of the data were taken from experiments not specifically 

 designed to study the effect of temperature. Only those in which the temperature did not 

 vary by more than ±1.0°C were used. In most cases the temperature fluctuation was much 

 less than this. 



>> Overt rhythmicity in luminescence is inhibited at this light intensity and is no longer 

 measurable after four periods. 



