<p>A device for generating a plurality of gas bubbles in a liquid. The device includes a conduit (58) adapted to carry the liquid. A first gas chamber (96) is formed near the conduit and an orifice (53) proximate a side wall of the conduit defines a passageway (60) between the first gas chamber and the conduit. A valve member (50) is adapted to seat against and close the orifice. The device may include a second gas chamber (86) and a diaphragm (36) responsive to gas pressure in the second gas chamber. A conduit (98) connecting the first and second chambers may include a variable vent (104) for controlling the size and number of gas bubbles injected into the liquid flowing in the conduit.</p>
