Progressive regeneration of excised mantle tissue in P. fucata is shown in Fig. 2. Rounding of the square ends of the wound occurred within 6 days (Fig. 2b). The length of the lesion was reduced by the anterior and posterior ends of the wound drawing closer together (Fig. 2c) to a point where further regeneration of the mantle was accomplished through extension of the central zone and formation of marginal tissue at the wound site to a point where it was continuous (Fig. 2d and e). The three lobes of the marginal zone were clearly visible by day 45 and complete regeneration of mantle tissue to its original extent was seen by day 60 (Fig. 2f).