An analysis is made of photoelectric photometry in the (J, B, V system ; of 10 Seyfert galaxies: NGC 1068, 1275, 3227, 3516, 4051, differ from ordinary ; spirals of the same morphological type in having a stronger central brightness ; concentration and a bluer color, especially in the central zone 5'' in diameter ; (excluding the nucleus itself). There is evidence that the ratio of H I mass to ;
... [Show full abstract] luminosity, and perhaps also the integrated mass/luminosity ratio, is smaller, on ; the average, for Seyfert galaxies than for normal spirals. If these properties ; are not transient ones, Seyfert-galaxy nuclei should continue their activity for ; a period considerably longer than kT = 10⸠yr, where T is the age of the ; galaxy and k is the proportion of Seyferts among ordinary spiral galaxies. ; (auth);