eggs are candled to observe the development of the embryo. candling is done in a darkened room with the egg held on a

egg veins observing duckling observation yolk incubator duck embryo lamp shining poultry development incubation inside developing darkness incubated candling heart brooding brooder light breeding red optical hatchling growing new unborn vasculogenesis biology research lab bird natural farm runner indian breed eggbearing closeup yellow domestic brightly