486 



RHYTHMS IN PLANTS AND ANIMALS 



Final "daurn" of 12:12 ryrlv prvitiitin/' liiiriiif: tlit rlitfmn iil 



"li/iirn" of dinpttiml t2-lnnir li^Ut nifiuiil 

 24 Uuur» itfitr li^ 



14 HOlM* 



Fig. 4. The effects on the Drosophila eclosion rhythm of single perturba- 

 tions with Hght. The histograms show the number of flies eclosing in 

 hourly intervals for 23 different cultures which have been exposed to a 12- 

 hr light signal at difl'erent times of the cycle of the rhythm as described 

 more fully in the text. 



