BrdU pulse and pulse-chase experiments with anterior regenerates at different time points. BrdU-labelled cells in green, mitoses in red; anterior is to the left. (A-G) BrdU pulse experiments are framed in white. (H-M) Pulse-chase experiments are framed in orange. (B-F) Anterior ends of posterior fragments show increased cell proliferation activity close to the wound site between 6 hours and 48 hours post-amputation. However, no head was regenerated. (I-M) The pulse-chase experiments tracked the gradual migration of BrdU-labelled cells into the tail plate. The two green spots in (M), indicated by white asterisks, are artefacts. Scale bars 100 μm.