Chick embryo head showing bone & cartilage

Head of an embryonic day 14 chick head stained with alcian blue and alizarin red to show cartilage (blue) and bone (red) development. At this stage there is already a considerable amount of bone in the jaw and the parietal bone, situated behind the eye, is now starting to form. The cartilaginous rings surrounding the trachea are also clearly visible.