part of part of existence starts during existence ends during stage 12 cilium apical tuft long immotile cilium elongated cilium A cilium of long size that does not contain molecular motors and as such does not exhibit any beating movement. In some echinoderms, long immotile cilia are found, when present, at the animal pole of embryos and constitute the apical tuft. echinoderm_anatomy long non-motile cilium larval development