We describe the serotonergic and cholinergic nervous system of the asexually reproducing acoel Convolutriloba longiWssura Bartolomaeus & Balzer, 1997 by means of immunohistochemistry, conventional histochemistry and transmission electron microscopy. Immunocytochemical staining for serotonin revealed neurons in the brain, in a pair of ventral main longitudinal cords, in two pairs of smaller dorsal longitudinal nerve cords, and in a submuscular nerve net. The brain comprises a ventral-anterior commissure and a less intensely stained dorsal commissure joined together by connectives into a three-ringed scaVold from which the longitudinal nerves extend. We followed the regeneration of the serotonergic part of the nervous system up to the second day after Wssion. Within this time period, the oVspring reestablished bilateral symmetry in the nervous system and developed full motor control. The presence of aminergic cell bodies associated with the main lateral nerve cords of C. longiWssura shows that the acoelan nervous system is more similar to that of other platyhelminths (triclads, rhabditophorans) than previously assumed. The presence of serotonergic cell bodies along the main nerve cord correlates with the capacity for asexual reproduction via Wssioning. We also describe the single Wssion mode of C. hastifera Winsor 1990, which brings the modes of asexual reproduction employed by members of the Convolutrilobinae to three.