Caenorhabditis elegans is a nematode worm. It has a small genome of only 6 chromosome pairs and 8x107 base pairs. It is hermaphroditic (self-fertilizing), making it easy to generate and identify recessive lethal mutations. The entire genome has been sequenced. Caenorhabditis elegans has a life cycle of only three days. The larva, consisting of only 560 cells (the lineage of each cell has been traced) hatches only 14 hours after fertilization.