The gradation extends even to the manner in which ordinary spines and the pedicellariae, with their supporting calcareous rods, are articulated to the shell.

In certain genera of star-fishes, "the very combinations needed to show that the pedicellariae are only modified branching spines" may be found.

Thus we have fixed spines, with three equi-distant, serrated, movable branches, articulated to near their bases; and higher up, on the same spine, three other movable branches.