Further observations of transport within paddle cilia.

Rhabdopleura has densely ciliated tentacles and cephalic shield. These cilia are of two sorts, ordinary cilia and those bearing paddle-like swellings. These swellings, about 1 micron across, are in the ciliary membrane. The axoneme bundle within the cilium remains intact, keeping the usual spatial arrangements, except that in the swelling its overall diameter is reduced. It is suggested that the mechanism for moving the paddle-like swellings along the length of the cilium is the releasing and reattaching of the side filaments from the axoneme to the ciliary membrane.