Trochosphere

Trochosphere, the name of a form of larva passed through by many worms and molluscs. It is a small free-swimming body. It consists of a comparatively large lobe in front of the month and a long tapering tail; at the base of the lobe is a ring of cilia, while another ring often occurs on the tail. The mouth is on the ventral surface, and leads to a short oesophagus, stomach, and intestine; the last opens to the exterior by an anus at the posterior end of the body. The body cavity of the 1arva is an archicoele (q.v.). The body of the adult is formed from the region behind the posterior circle of cilia; the rest of the larva is absorbed or thrown off.