Extraction of frog retinas in acidified Ringer solution reveals an average Ach content of 3.4 γ/g in light-adapted and 3.6 γ/g in dark-adapted frogs. Direct comparison of Ach activity in extracts of lightand dark-adapted retinas, without reference to absolute magnitudes, also reveals no difference to absolute magnitudes, also reveals no difference greater than the error of the method. The lack of significant difference is in accord with the work of Therman, but not with that of Lange who finds a tenfold increase upon dark adaptation.