[Ultrastructure of the tegumnet of the slow-growing larva of Polystoma integerrimun (Frohlich 1798). Evolutionary significance].

The ultrastructure of the integument of the gill living post-larva of Polystoma integerrimum (Monogenea) from the common frog Rana temporaria is investigated for the first time; it has been compared with those of the adult stage, of other juvenile stages of marine Monogenea and of some Digeneans adapted to frog urine.