[v. 1.] Protozoa through Ctenophora.
v. 2. Platyhelminthes and Rhynchocoela, the acoelomate Bilateria.
v. 3. Acanthocephala, Aschelminthes, and Entoprocta, the pseudocoelomate Bilateria.
v. 4. Echinodermata, the coelomate Bilateria.
v. 5. Smaller coelomate groups.
