The surface of the eggshells of the Helmeted guinea fowl (Numidia meleagris) was polished during incubation by the parent. Examination with the light microscope showed that the cuticle had been removed from the ridges on the outer surface of the shell and that the plugs in the outer orifice of the pore canals had acquired extraneous materials including grease. Studies with a scanning electron microscope revealed that the spheres that made up the pore plugs retained their identity even though they were stained. It was concluded that ridges on the shell surface protected the pore plugs from damage by attrition and that the plugs acted as filters thereby preventing nest debris from occluding the pore canals or contaminating the shell membranes.