Ciliogenesis, ciliary function, and selective isolation.  In addition to their classic role in cell motility, certain cilia have sensory or signaling functions. In sea urchin embryos, short motile cilia randomly propel the early embryo, while a group of long, immotile cilia appear later, coincident with directional swimming and localized within a region that gives rise to the larval nervous system. Motile cilia can be selectively removed by treatment with a novel derivative of dillapiol, leaving the putative sensory cilia for comparative investigation and a gently deciliated embryo ready for studies of regeneration signaling.