| A medusa, or jellyfish, is part of the life cycle of just one major group of animals, the cnidarians. |
| If collar cells and spicules are defining characteristics of the Phylum Porifera, then nematocysts define cnidarians. |
| Casually touching many cnidarians will make it clear how they got their name when their nematocysts eject barbed threads tipped with poison. |
| In the cnidarians, chaetognaths, and ctenophores, the opaque gut wall was the surface measured. |
| Fossils of the Twitya Formation are generally presumed to be cnidarians, or at least metazoans of cnidarian grade. |
| The planulae of most cnidarians attach and lose, at most, a coat of swimming cilia. |
