GUSTOIMAGES / SCIENCE PHOTO LIBRARY GUSTOIMAGES / SCIENCE PHOTO LIBRARY
Bird egg and embryo. X-ray of an egg with an 21-day-old bird embryo developing inside. This is a well-developed embryo near full term. The X-ray shows the bones of its skeleton, with the skull at bottom, the backbone at left, wing and leg bones at centre and right, and a foot at top. Typical incubation periods for eggs such as those laid by chickens are around 20 days, though in other species the incubation period can range from 10 to 45 days.
Model release not required. Property release not required.