The mycelium is coenocytic and produce septa only to separate the reproductive structures from the assimilative portion of the thallus.
Asexual reproduction is by zoospores that are produced in zoosporangia.
The zoospores produced are biflagellated with one flagellum of the whiplash type and the other of the tinsel type. A swimming sperm is absent in the Oomycota. This type of sexual reproduction is referred to as gametangial copulation . The eggs and sperms are products of meiosis and the only parts of the life cycle that are haploid. Only one class, the Oomycetes, is recognized in this division.