BACTERIAL PHOTOSYNTHESIS 201 



A working hypothesis should represent a balance between sim- 

 phcity and concrete suggestions. Our simplified model (Fig. 11) 

 satisfies this criterion, but testing by prediction is needed to assess 

 its utility. 



Note Added in Proof 



W. Arnold and R. K. Clayton have obtained evidence with chro- 

 matophore films ( Proc. Nat. Acad. Sci. U.S. 46: 769-776; 1960) that 

 the first step in photosynthesis appears to be the separation of an 

 electron and a hole in a chlorophyll semiconductor. The data sup- 

 port our hypothesis of the ultrastructure of the chromatophore. 



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