The results of experiments on the stroboscopic observation of the domain structure and measurements of the hysteresis loops of an iron garnet film with a moderate perpendicular anisotropy in a harmonic ac field in the range of frequencies f = 0.2-7.0 kHz and amplitudes H(0) = 0-170 Oe are presented. The dynamic domain structures observed are shown to correspond to concrete segments of magnetic-hysteresis loops. New forms of dynamic domains, which were called dendritic, have been revealed.