tailAs in all vertebrates, the fish tail bud begins to form immediatelyfollowing gastrulation, followed by a pattern of extension, protru-sion, and eversion away from the yolk cell. The post-anal axialbody of fish larvae is extended posteriorly and both somites andfin folds are symmetrical about the longitudinal axis (Fig. 2). How-ever, within three days after hatching, this axial symmetry is lost asthe ventral portion of the developing tail grows rapidly, displacingthe notochord at an angle dorsally (Potthoff et al., 1988; Bird andFig