A cartridge detachably mountable to a main assembly of an image forming apparatus includes a photosensitive drum; a discharging path for permitting movement of a developer removed from the drum, the discharging path including a developer discharge opening and a movable portion through which the developer is movable and which is movable between a retracted position in an upstream side with respect to a developer moving direction through the discharge opening and a advanced position in a downstream side with respect to the developer moving direction; and a sealing portion for closing the discharging path by contacting the movable portion at a position different from that of the discharge opening.