1. An analogous operation was performed in chick embryos (St. 19 to 23) byJ. W. Saunders andM. T. Gasseling (Anat. Rec.121, 360 [1955]) to study the symmetry relations of wing parts. In one case (out of 13) supernumerary segments formed in the distal part of the wing.
2. R. Amprino andM. Camosso, Arch. Biol.67, 613 (1956); Roux, Arch. (1958), in press.
3. J. W. Saunders, Anat. Rec.105, 567 (1949).
4. E. Zwilling, J. exp. Zool.132, 157 (1956).