In trematodes, one egg normally leads to the production of many offspring!  The egg (1) of most forms is oval and has a lid-like hatch called an operculum. Eggs are deposited in water via the feces of the definitive host.   When they reach freshwater, the operculum opens and a ciliated free-swimming larva called a miracidium (2)  swims out.  The miracidium will then swim about until it finds a suitable intermediate host, which is usually an aquatic snail (8) to  which it is chemically attracted.  When the miracidium finds snail, it penetrates it, loses its cilia and develops into a sporocyst (3), which produces asexually either more sporocysts or a number of rediae (4). These rediae produce asexually either more rediae or tailed forms called cercariae (5). The cercariae emerge from the snail, swim around and penetrate a second intermediate host, the final host or encyst on vegetation, where they are transformed into metacercariae (6), which are juvenile flukes; the adult (7) grows from the metacercariae when it is eaten by the definitive (final) host.