Ontogeny: development of an individual
from the moment the egg is fertilized up till adulthood.
Opaque area: non-transparent part.
Pellucid area: transparent part.
Neural fold: fold related to the head.
Neural tube: extension related to the head.
Heart: blood-pumping organ.
Omphalomesenteric arteries: vitelline duct.
Wing buds: beginning of the formation of the wings.
Limb buds: beginning of the formation of the legs.