Prospective fates and regulative capacities of fragments of the female genital disc of Drosophila melanogaster.

A fate map of the female genital disc of Drosophila melanogaster was established by examining the derivatives of fragments transplanted into host larvae for metamorphosis. The fate map is presented as a two-dimensional projection, but for several reasons it is proposed that the anal plates originate from the dorsal epithelial layer whereas the genitalia are produced from the ventral layer. Fragments produced by cuts parallel to the axis of symmetry of the disc undergo regeneration during culture in adult hosts if the fragments comprise more than half of the disc, or duplication if they comprise less than half. Most of the fragments generated by bilaterally symmetrical cuts across the line of symmetry of the disc undergo neither regeneration nor duplication during culture, but with some such fragments there is a low frequency of regeneration. It is argued that the usual lack of regeneration in these fragments results from wound healing which confronts identical positions from right and left sides, giving no growth stimulation. The fragments which regenerate might do so as a result of healing between dorsal and ventral surfaces, providing the discontinuity in positional information which is thought to be involved in growth stimulation.