2021-8-24 · 1. Clitellum, 2. Genital setae (segment 26). During mating, the pair of genital setae are used to help bind two worms together while facing in opposite directions. 3. Sperm grooves As two worms mate, sperm released at the sperm ducts travels in the worm''s sperm grooves to the seminal receptacle opening of the other worm. 4.