Do the galaxies NGC 936 and NGC 3198 possess massive spheroidal subsystems?

The condition for gravitational stability of the stellar disks of the galaxies NGC 936 and NGC 3198 makes maximum disk models unacceptable. We present mass estimates for these objects' spheroidal components. The mass of the dark halo of NGC 3198, within four disk radial scale lengths, exceeds its disk mass by a factor of 1.6 to 2. The masses of the disk and spheroidal subsystem (halo + bulge), within four radial scale lengths, are approximately the same for NGC 936.