The upper part of the antheridium becomes separated from the parent stem by a septum, and its contents are converted into ciliated motile antherozoids.

The upper part of the antheridium becomes separated from the parent stem by a septum, and its contents are converted into ciliated motile antherozoids.

The antheridia are stalked sacs, with a single wall of cells, and the spiral antherozoids arise by free-cell formation from the cells of the interior.