Bryopsis monoica from Banyuls appeared to have a heteromorphic biphasic life-history. Zygotes from anisogametes grew into creeping filamentous germlings (the sporophytic phase) that produced stephanokontic zoids. The stephanokontic zoids directly developed into new Bryopsis thalli (gametophytic phase). The cell walls of the gametophytic phase positively stained with zinc-chlor-iodine and Congo red, whereas the cell walls of the sporophytic phase did not.