have to be 10-15 seconds. A reasonable figure for the collision broadening of the excited level would be given by r ' 1013 sec1. Since the chlorophyl molecules are thought to be arranged in a monomolecular layer. we let n = 2, then t, 2 X 10-3. n2 Therefore the condition for convergence of the perturbation series is by no means fulfilled, and in order to get a valid approximation, one would have to solve the secular equation. which would lead to nonlocalized states. Further work in this direction is in progress.The above considerations hold also for more extensive systems. It seems possible that they can be applied to biological processes other than photosynthesis. For example, excitation processes in the retina could be mentioned. The light wave focused on one visual rod is coherent within the area of this rod. It s:ems probable that this collective character of the excitation is important for the formation of the signal in the adjoining nervous system. It also seems possible that collective activities play a role in the function of the central nervous system and relations may be found, say, between conscience and nonlocalized electronic states, or S and storage of memory.

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Results of studies on the effect of dietary P deprivation on pig renal 1 alpha- and 24-hydroxylase activities and on concentrations of plasma alkaline phosphatase, Ca, P and vitamin D metabolites are presented. Renal 1 alpha-hydroxylase activity was increased six- to eightfold and plasma 1,25-dihydroxyvitamin D3 concentration increased two- to threefold in pigs fed a low P diet (.085% P) compared with pigs fed a control diet (.6% P). In contrast, renal 24-hydroxylase activity and plasma 25-hydroxyvitamin D concentration did not differ between diet groups. Plasma alkaline phosphatase activity was two to four times higher in pigs fed the low P diet compared with pigs fed the control diet. The rate of gain by pigs fed the low P diet was less than pigs fed the control diet. The low P diet was associated with a prolonged elevation of renal 1 alpha-hydroxylase activity in spite of the presence of a pronounced hypercalcemia.