A pipette for repeatedly aspirating and dispensing a predetermined quantity of liquid. The pipette includes a hollow body having first and second extremities. The second extremity is adapted to removably receive the pipette tip. An ejector is carried by the body and has a first extremity disposed within the first extremity of the housing and a second extremity movable vertically about the second extremity of the housing. The ejector is movable from a first position for permitting the pipette tip to be securely mounted on the second extremity of the housing and a second position for pushing the pipette tip off of the second extremity of the housing. A spring is carried by the housing and is compressed so as to store energy in the spring. A locking mechanism is additionally carried by the housing for retaining the spring in the compressed position. The locking mechanism is releaseable so that the ejector is driven by the spring to the second position to move the pipette tip distally on the second extremity of the housing.