After resting, the nucleus of the zygote divides by meiosis to form immature protoplasts with 4-16 haploid nuclei. They have half +strain and half -strain properties. Each aborted protoplast develops into a flagellated spore. They are called meiospores as they are produced by the process of meiosis. Zoospores and aplanospores germinate under favorable conditions to form new filaments of Ulothrix.