By a process of infolding, the thicker end is partially invaginated, the middle portion or " hind-body " and the organism may now present a superficial likeness to a cercaria.
D, An adult redia, containing a daughter-redia, two almost mature cercariae, and germs. E, A free cercaria.
It escapes into the adjacent tissue and there gives rise either to one or more generations of rediae or at once to a new type of organism - the cercaria.
What determines the origin of the cercaria rather than a new generation of rediae is unknown.
The cercaria is just visible to the naked eye and has an oval or discoidal body and usually a long tail of variable form.