Thus, although isogamy consists in typical cases of a union of naked motile gametes by a fusion which begins at the beaked ends, and results in the formation of an immotile spherical zygote surrounded by a cell-wall, in Leptosira it is noticeable that the fusion begins at the blunt end; in a species of Chlamydomonas the two gametes are each included in a cell-wall before fusion; and in many cases the zygote retains for some time its motility with the double number of cilia.
Chlamydomonas pulvisculus, Ehr.
Chlamydomonas sp., unicellular; chr.,chromatophore; p.,pyrenoid; H.
Again, many Green Algae - some unicellular, like Sphaerella and Chlamydomonas; some colonial forms, like Volvox and Hormotila: some even filamentous forms, like Ulothrix and Stigeoclonium- are known to pass into a condition resembling that of a Palmella, and might escape identification on this account.
Conjugation of adults has been observed in several species, the most complete account being that of Zederbauer on Ceratium hirundinella (marine): either mate puts forth a tube which meets and opens into that of the other (as in some species of Chlamydomonas and Desmids); the two cell-bodies fuse in this tube, and encyst to form a resting zygospore.