In metamerism, there is serial repetition of unit subdivisions of:
| I. | Ectoderm products |
| II. | Mesoderm products |
| III. | Endoderm products |
| 1. | Only II | 2. | Only I and II |
| 3. | Only II and III | 4. | I, II and III |
Parazoa is a taxon at the base of the phylogenetic tree of the animal kingdom and includes the most primitive forms, characterized by not having proper tissues. The phylum/phyla included in this taxon will be:
| I. Porifera | II. Cnidaria | III. Ctenophora |
| 1. | Only I | 2. | Only II and III |
| 3. | Only I and II | 4. | I, II and III |