Abstract: A portable incubator having an open top jar which is closed by a lid secured to the jar by a releasable clamp. The lid has a conduit on its upper surface, the conduit communicating with a hole through the lid and provided with a pair of opposed ends. There is a valve for each end of the conduit, respectively. A holder for culture dishes can be moved into and out of the jar, the holder being formed by a number of rigid straps arranged to form a side opening in the holder so that the culture dishes can be put into the holder and supported on the bottom of the same. A hand-held, hand-actuated vacuum pump can be carried with the jar and has a flexible tube connecting it to one end of the conduit so that the interior of the jar can be evacuated in a short time. The opposite end of the conduit is adapted to permit a gas to be injected into the jar under pressure after the jar has been evacuated.