Cell contents cleave to produce unicellular, biflagellate zoospores or gametes. Unlike the zoospores the gametes are not released but lose their flagella and produce miniature colonies within the mother cell wall.

The similar sized gametes fuse to form a zygote and these become thick-walled and angular. After a rest period each produces 2-5 zoospores each of which becomes an enlarged polygonal cell whose contents divide into flagellated cells which produce a new miniature colony.

The miniature nets are released by gelatinisation of the cell wall.