In Mud Gas separator, the mud, which has been returned from a borehole, is forced to flow upwardly through a main cylindrical housing by the action of an auger device. The auger flight is spaced from the auger shaft, so that a longitudinally extending, axial passageway is formed within the housing for removal of gases from the mud. The auger flight is comprised of a plurality of sections, each axially spaced from one another, with a perforated member being interposed therebetween. The combined action of the flight and the perforated member causes the mud to assume a flow path which releases an unexpected amount of gas therefrom. An annular trough at the top of the housing collects the degasified mud. A closure member at the upper end of the housing enables the axial passageway to be evacuated which enhances the removal of gases from the mud.