A Petri dish, which consists of a receptacle and of an additional lid, which both have a revolution shape and which are each delimited by a bottom wall (20; 30) and at least one peripheral wall (21; 22; 31), - a wall (21; 22; 31) of the receptacle or respectively of the lid bearing at least two angularly equidistant fingers generally parallel to the bottom wall (20; 30), which radially protrude towards the wall (31; 21; 22) of the lid or respectively of the receptacle, - while the wall (21; 22; 31) without any fingers bears a same number of locking members provided with a cam path able to receive said fingers, - this receptacle and this lid may selectively occupy either one of the successive different positions indicated below: a/ a first position, so-called "non-locked beforehand" position, in which said fingers are not received in said locking members; b/ at least one "intermediate position" selected from: - a "non-ventilated locked" position, in which said fingers are received in said locking members and in which the receptacle is in intimate contact with the lid, so that the internal space which they delimit is isolated from the outside medium, and - a "locked and ventilated" position in which said fingers are received in said locking members and in which the receptacle is not in intimate contact with the lid, so that the internal space which they delimit is not isolated from the outside medium; - c/ a "final position", so-called "read out" position, in which said fingers are released from said locking members and allow lifting of said lid, the passing from one position to the next position being accomplished at least by a relative rotation of the lid relatively to the receptacle, in a same direction, characterized by the fact that said locking members bear at least one means (53; 7) for blocking the fingers in an "intermediate position", which opposes the return to the "first position", while allowing passing to the next position. - a wall (21; 22; 31) of the receptacle or respectively of the lid bearing at least two angularly equidistant fingers generally parallel to the bottom wall (20; 30), which radially protrude towards the wall (31; 21; 22) of the lid or respectively of the receptacle, - while the wall (21; 22; 31) without any fingers bears a same number of locking members provided with a cam path able to receive said fingers, - this receptacle and this lid may selectively occupy either one of the successive different positions indicated below: a/ a first position, so-called "non-locked beforehand" position, in which said fingers are not received in said locking members; b/ at least one "intermediate position" selected from: a/ a first position, so-called "non-locked beforehand" position, in which said fingers are not received in said locking members; b/ at least one "intermediate position" selected from: - a "non-ventilated locked" position, in which said fingers are received in said locking members and in which the receptacle is in intimate contact with the lid, so that the internal space which they delimit is isolated from the outside medium, and - a "locked and ventilated" position in which said fingers are received in said locking members and in which the receptacle is not in intimate contact with the lid, so that the internal space which they delimit is not isolated from the outside medium; - c/ a "final position", so-called "read out" position, in which said fingers are released from said locking members and allow lifting of said lid,