unc-18 expression in the male gonad and ventral nerve cord. Nomarski (A, D), fluorescence (B, E) and merged (C, F) images of unc-18::YFP expression in the male gonad region and part of the ventral nerve cord. (A–C) Lateral view; (D–F) dorsal view. The dashed arrow indicates the sperm in the seminal vesicle, and the solid arrow indicates the valve area where the sperm exit into the vas deferens. Arrowheads in (A–C) indicate the ventral nerve cord.