Genetical Studies on the Skeleton of the Mouse

Following the discovery of the ventral ectodermal ridge of the tail in mouse embryos (Grüneberg, 1956), it became necessary to test its possible influence on tail development in those mutants whose effects on the axial skeleton are traceable to the 10–11-day stage, i.e. to the period when the development of the ventral ectodermal ridge (V.E.R.) is at its height. In the case of vestigial-tail (vt/vf, Grüneberg, 1957), virtual absence of the tail was associated with a marked reduction of the V.E.R. to one-quarter or less of its normal size. In Danforth's short-tail (Sd/ + and Sd/Sd; Grüneberg, 1958), on the other hand, reduction or absence of the tail was accompanied by no more than a slight reduction in size of the V.E.R. The present paper deals with Brachyury (T/ + and T/T) and with Anury or taillessness (T/t6 and T/t1 respectively). Short-tail or Brachyury is a semidominant condition lethal in homozygotes (Dobrovolskaia-Zavadskaia, Kobozieff, & Veretennikoff, 1934; Kobozieff, 1935).