156 



PHOTIC SENSITIVITY OF CIONA INTESTINALIS 



photic reaction proceeds according to the Bunsen-Roscoe rule as in- 

 dicated in equation (1). It is, that, with a given intensity of illu- 

 mination, the sensitization period indicates the quantity of stimulus 

 received by the animal. The photochemical effect (£) will vary with 

 the duration of the exposure {t) when the intensity (/) is constant. 



/z 



/o 



I 



2.1 



.0 



It; 

 I 



V 



/.J 



as 



0.1 



I 



o 2O0O Aooo 6000 aooo /o,ooo 



Light Inteos/fu—^ Cand/e-meters 



Fig. 1. Curve A gives relationship between intensity of light and reaction 

 time of Ciana. This curve is an hyperbola as is shown by Curve B representing 

 the relation between the reciprocal of the sensitization period and intensity. 



The reaction time at any moment may therefore be used as a measure 

 of the amount of photochemical effect necessary in order to act as a 

 stimulus in the sense organ. In this way we may investigate the 

 sensitivity of Ciona under different conditions in order to gain a 

 clearer insight into the photochemical process which underHes it. 



