The ventilations were examined on the Pen-shell, Atrina (Servatrina) lischkeana, the Japanese oyster, Crassostrea gigas, the Rock-oyster, C. nippona, the Densely lamellated oyster, Ostrea denselamelloosa, the Mediterranean blue mussel, Mytilus galloprovincialis, the Asian brown mussel, Modiolus metcalfei, by recording simultanenously the water-volumes inspired and expired through mantle cavity. The water-volumes in those animals synchronously changed. The results exceedingly proved that the inspiration and the expiration synchronized when the suspension-feeding bivalves ventilated.