ABSTRACT
A study of the embryology of female-sterile mutants can provide information on the course of normal development, particularly when several mutants affect the same organ system. A favourable situation for an investigation of this kind arises with the formation and migration of the pole cells in Drosophila species. A number of genetic characters are known whose expression in the embryology of the offspring of affected mutant females involves the complete loss of pole cells or a change in their distribution after gastrulation. Thus the sex-linked female sterile mutant fs nasA (Counce & Ede, 1957), and the sex-linked lethals Lf11 (Ede, 1956a), X2 (Ede, 1956b), X27 (Ede, 1956c) and X10 (Ede, 1956d) all show disturbances of the pole cell complement.
