Commercial breeders often used to seperate eggs from different matings inside the hatcher by placing them in Muslin bags, or by placing them into small wire mesh container-like cages. I have managed to seperate eggs by making cardboard 'dividers' that contain the chicks as they hatch, however, it's as well to ring or mark the hatchlings as soon as possible as they are born escapologists and there's nearlly always one that very quickly seems to find a way out of it's cardboard corral, no matter how high or well put together it seems!!