  Magnetic bubbles are remarkable spin structures that developed in uniaxial
magnets with strong magnetocrystalline anisotropy. Several contradictory
reports have been published concerning the magnetic bubble structure in a
metallic magnet MnNiGa: Biskyrmions or type-II bubbles. Lorentz microscopy in
polycrystalline MnNiGa was used to explain the magnetic bubble structure.
Depending on the connection between the magnetic easy axis and the observation
plane, two types of magnetic bubbles were formed. Magnetic bubbles with
180{\deg} domains were formed if the easy axis was away from the direction
perpendicular to the observation plane. The contrast of biskyrmion is
reproduced by this form of a magnetic bubble. When the easy axis was
approximately perpendicular to the observing plane, type-II bubbles were
observed in the same specimen. The findings will fill a knowledge gap between
prior reports on magnetic bubbles in MnNiGa.
