218 CONTROL MECHANISMS IN CELLULAR PROCESSES 



as in man)' other insects, is photoperiodically controlled. An ap- 

 parently complete blocking of vision has little or no effect on the 

 response. 



In summary, our questions about the photoreceptor pigments in 

 animal photoperiodism, and the possible presence of the red, far-red 

 system, stay unanswered. Thev will remain so until adequate action 

 spectra are available and until the visual and non-visual components 

 can be distinguished. One should note here that some of the data 

 relating the red, far-red system to the rate of oxidative phosphory- 

 lation, mentioned previously, have been obtained with rat-liver 

 mitochondria (Gordon and Surrey, 1960). Although a temporary 

 suspension of judgment seems called for, at least the visual com- 

 ponent is eliminated in this case. 



Before leaving this subject, I cannot resist mentioning a recent 

 paper (Ballard, 1958) on the phototactic response of the stable fly, 

 Stomoxys calcitmns: There are several peaks in the action spectrum, 

 including a very distinct one at about 6400 A. In addition, light of 

 about 7300 A has a clearly opposite— repellent— effect and is the 

 only region that does so. Yet, oddly enough, there is no evidence 

 for the presence of pigments with absorption peaks at those wave- 

 lengths in the eye itself. It is barely possible that some of these 

 results may be due to slight temperature differences, but it is also 

 tempting, at least to those of us who see the red, far-red system 

 under every bed, to see it here. Unfortunately, the author, who 

 himself was puzzled by these results, was apparently unaware of the 

 existence of the red, far-red pigment and thus did not examine the 

 possibility further. 



If some of what has been said so far sounds like a criticism of 

 other biologists for not doing photoreceptor research as successfully 

 as plant physiologists, the next topic could not even suggest such a 

 tone. Perhaps the majority of non-visual, non-photosynthetic light 

 effects on all organisms have action spectra with maxima in the blue 

 or blue-green. It is probably safe to say that these are no better 

 understood now than they were some 20 years ago, although we can 

 suggest more possible mechanisms and also more possible pitfalls. 

 Before examining these, let us list some of the phenomena which 

 are known, or may be reasonably suspected, to be affected by blue 

 light. These include phototropism in higher plants and in fungi 

 (Banbury, 1959; Galston, 1959; Reinert, 1959; Went, 1956); pho- 



