ABSTRACT
In the known examples, the supernumerary radial canals of multiarmed species of asteroids form either before or after metamorphosis (whether the number of supernumerary arms is constant or variable), but never both, before or after metamorphosis in the same species. Except for species of the genus Luidia, which form the supernumerary radial canals either before or after metamorphosis, species that form the supernumerary radial canals before metamorphosis have direct or non-brachiolarian development while those that form them after metamorphosis have indirect development. This latter group includes species with a large number of arms. The length of the period of formation of supernumerary radial canals varies with species. The coefficient of variation increases with the number of supernumerary canals.
