 It lays eggs which pass with the fish faeces out into the sea and which hatch into free-swimming larvae, the coracidium.For development to proceed, the coracidium must be swallowed by a copepod, after which it develops into the infective stage, the plerocercoid.If the copepod is then eaten by a small fish, such as a goby, the plerocercoid survives in its digestive tract.