ABSTRACT
The sequence of appearance of different structures during regulation was ascertained for three wing disc fragments. It was found that structures were added sequentially from the cut edge. Regeneration in one fragment was very fast and successful, and it is suggested that this is difficult to explain in terms of wound healing being responsible for the decision to regenerate rather than duplicate. In another fragment, regeneration appeared to proceed from one part of the cut edge only, this being the region through which the anteroposterior compartment boundary runs. Compartment boundaries have been implicated in both proximodistal and circumferential regeneration, and it is suggested that regeneration is controlled at these sites. The decision to regenerate rather than duplicate may be made on the basis of which compartment boundaries are exposed at the cut edge, and their preferred direction of regeneration. The implications of this interpretation for the control of growth are discussed.
