In automatically designing a base sequence to be used as a probe which is hybridized with an unknown nucleic acid fragment to perform gene analysis, a discrimination tree in which a plurality of partial base sequences obtained from target base sequence data are arranged on nodes is generated. A guide member defines a first guideway along which moves a first slide member, the latter in turn defining a second guideway parallel to the first, along which a second slide member moves. The tests allow to anticipate and hence prevent hazardous opening of barriers due to a faulty zero speed indication. A pump coupled to the manifold is located external to the tank and is heated by the manifold heater.