2 longitudinal blood vessels, dorsal and ventral. Gas exchange through skin. O2 carried by hemoglobin. Excretory system has paired metanephridia in almost every segment. The ciliated funnel dumps into the next anterior cavity.
Cerebral ganglia are above and below pharynx.
Thick mucus of clitellum glues worms together. Sperm stored in seminal vesicles Clitellum later secretes membranous cocoon that moves toward head. Cocoon has sticky fluid and eggs inside, sperm added as it moves forward Cocoon moves over head and the openings close to a spindle-shaped capsule that protects developing worms from drying out. Most are blood-sucking parasites, some are predators. Think of politics.