The nervous system of one very small roundworm, the nematode "Caenorhabditis elegans", has been completely mapped out in a connectome including its synapses. Every neuron and its cellular lineage has been recorded and most, if not all, of the neural connections are known. In this species, the nervous system is sexually dimorphic; the nervous systems of the two sexes, males and female hermaphrodites, have different numbers of neurons and groups of neurons that perform sex-specific functions. In "C. elegans", males have exactly 383 neurons, while hermaphrodites have exactly 302 neurons.