Recessive Rumplessness of Fowl with Kyphoscoliosis and Supernumerary Ribs.

URING 1937 some abnormal chicks appeared among the progenies of two D different breeding pens of our experimental flock of fowls. These chicks showed a close outward resemblance to specimens of the dominant rumpless variation and its intermediate modifications (DUNN 1925; LANDAUER and DUNN 1925; LANDAUER 1928). The simultaneous occurrence of a number of such rumpless birds suggested that we were dealing with a hereditary condition. There was no relationship to our dominant rumpless stock. The parents of these new rumpless chicks all had entirely normal skeletons. It appeared, therefore, that we were dealing with a recessive mutation. Experiments were undertaken in order to learn something about the mode of inheritance and the morphological expression of the new mutation, and the results are to be reported here. A brief preliminary notice of this work was published in 1942.