This work is a contribution to the comparative morphology of the bird's skull, particularly to current knowledge of the development of the chondrocranium. It comprises the detailed description of nine developmental stages leading up to the fully formed chondrocranium. Problems and conflicting interpretations concerning certain aspects of the avian chondrocranium are discussed and evaluated, and areas needing further investigation are outlined. The volume also gives a comparison with the results of Lang to point out interesting parallels and differences.