a, Electron micrographs of a representative chemical synapse (left) and a gap junction synapse (right), marked by an asterisk. The triadic chemical synapse of AIYR to RIAR, AIZR, and RIBR (synapse number N2U391) is recognized by the presynaptic density and the presence of presynaptic vesicles within AIYR. The postsynaptic cells are entered into the database in a clockwise order around the presynaptic density. As electron micrographs give a consistent cross-sectional view from the posterior, the location of the neuronal processes is oriented in the worm. The gap junction (synapse number N2U3875) is recognized as a straightened or slightly curving region of apposed membranes with increased staining and a uniform small gap. Below the micrographs is shown how each of these two synapses is listed in the table of synapses (Supplementary Information 3). b, Number of postsynaptic partners at chemical synapses. The lower number of polyads in the male data is probably not a true difference between the sexes, but rather a result of the less-complete nature of the male reconstruction, which was due to the lower quality of the electron micrographs. c, Size distributions of synapses. d, Larger edges are composed of larger synapses as well as more synapses.