Fig. 4. Structural aspects of the notochord. (A) A lateral view of a living zebrafish tail at 24 hpf, showing the main features of the notochord. Dorsal to the notochord is the floor plate, in the ventral-most part of the forming spinal cord. Ventral to the notochord is the hypochord. (B) A schematic diagram of lateral and cross-sections of the notochord, showing the floor plate and hypochord acting as cables running along the top and bottom of the notochord. (C) As well as the notochord, the floor plate and hypochord express type II collagen (Yan et al., 1995). cc, central canal; fp, floor plate; hy, hypochord; no, notochord; nt, neural tube.