An apparatus (2) for the automatic testing of substances for carcinogenicity comprises: a plate support (3) on which at least one micro-well plate (1) can be placed; a movable pipetting unit (4) comprising a predetermined number of pipettes (40); a number of containers (5) containing a liquid culture medium (50), the number of containers (5) corresponding to the number of pipettes (40) of the pipetting unit (4); a dish support (6) on which a corresponding number of dishes (60) can be placed, each having a bottom and an upstanding side wall (601); a plurality of spinners (63) for spinning the dishes (60); a plurality of suction cups (62) for placing a lid (600) on each of the dishes; and a plurality of laterally arranged belts (64,65) for transporting the closed dishes (60) to an intermediate storage (8).