eukaryotic microorganisms (the single-celled protists and their multicellular descendants). All eukaryotic organisms with the exception of animals (developing from diploid blastulas), plants (developing from embryos supported by maternal tissue), and fungi (developing from zygo-, asco-, or basidiospores) are protoctists. Protoctists include two-kingdom system "protozoans" and all "fungi" with mastigote stages as well as all algae (including kelps), slime molds, slime nets, and other obscure eukaryotes.

Alternative forms for protoctist : Protoctista, protoctists.