eggs are candled to observe the development of the embryo. the hand holds a duck egg over the light source. visible

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