Abstract 1. 1. Photographs and diagrams are presented of the location of the cells containing 5HT in the supra- and sub-oesophageal ganglia, segmental ganglia and adbominal ganglia. 2. 2. The semental ganglia each contain seven cells with 5HT (not six as previously described). 3. 3. Cells containing catecholamines are found in the supra- and sub-oesophageal ganglia, the first free ganglion of the nerve cord, the abdominal ganglion and the anterior lateral nerve. 4. 4. The physiological role of the catecholamines and indolealkylamines in discussed.