| Hox genes have been isolated from a number of cnidarian species including hydra. |
| The earliest expression of Hox genes for these arthropods is in the already formed segmental anlage, in the presumptive position of the developing segment. |
| The Hox genes exert this influence by their action on the genes controlling the development of these structures. |
| Across major phylogenetic comparisons, the evolution of Hox clusters generally parallels the evolution of axial complexity. |
| We have isolated and sequenced eight Hox genes from the freshwater triclad Girardia tigrina and three Hox and two ParaHox genes from the polyclad Discocelis tigrina. |
| Hox evidence has also placed dicyemid mesozoans in the clade. |
