Ablation of amphid sheath cells results in behavioral and developmental deficits, including an inability to form dauers in the presence of the pheromone (Bargmann et al., 1990; Vowels and Thomas, 1994). The amphid neurons are then unable to take up FITC in these animals. Sensory function becomes impaired following amphid sheath ablation, even after the sensory organ has formed. Although amphid neurons continue to survive in these animals, their dendritic tips show morphological abnormalities, suggesting a function for the sheath cells in maintenance of amphid ciliary properties