Abstract: An internal combustion engine includes a body defining at least a portion of a combustion chamber. The combustion chamber is adapted to receive a combustion mixture. A cavity in the body has an open end in fluid communication with the combustion chamber. The cavity is adapted to receive a portion of the combustion mixture in the combustion chamber through the open end such that substantially all of the combustion mixture received in the cavity is the combustion mixture received from the combustion chamber. An ignition source resides in the cavity at an end opposite the open end. An apertured member is adjacent to the ignition source and has one or more apertures therein. The apertures are operable to allow passage of the combustion mixture to the ignition source and, upon ignition of the combustion mixture in the cavity, jet a portion of the ignited combustion mixture into the combustion chamber.