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.
Somites: metameres.
Omphalomesenteric arteries: vitelline duct.
Wing buds: beginning of the formation of the wings.
Limb buds: beginning of the formation of the legs.

Photo :

EN : Feet of ostrich
FR : Pieds d'autruche
ES : Pies de avestruz

          of ostrich

Its feet of ostrich are very curious, and different from those of all other birds. They are somewhat like the foot of the camel, having a soft pad or cushion underneath, and only two toes. The largest toe is about seven inches long, and has a broad claw at the end; the other is about four inches long, and has no claw. Although ostrich cannot fly, it can run faster than the swiftest horse.

Animation : Bird's eggs

Thanks to YouTube for allowing us to watch this video.