Imperium naturæ C. Linnaeus, 1758 - nature
   Mundus Plinius - physical world
     naturalia - natural bodies
       Regnum Animale C. Linnaeus, 1758 - animal kingdom see Kingdom Animalia Linnaeus, 1758
         Class Vermes Linnaeus, 1758 - worms see Phylum Vermes (C. Linnaeus, 1758)
           Order Zoophyta Linnaeus, 1758
             Genus Hydra Linnaeus, 1758
               01 Hydra polypus Linnaeus, 1758
               02 Hydra campanulata Linnaeus, 1758
               03 Hydra socialis Linnaeus, 1758
               04 Hydra stentoria Linnaeus, 1758
               05 Hydra pyraria Linnaeus, 1758
               06 Hydra convallaria Linnaeus, 1758
               07 Hydra crataegaria Linnaeus, 1758
               08 Hydra opercularia Linnaeus, 1758
               09 Hydra umbellaria Linnaeus, 1758
               10 Hydra berberina Linnaeus, 1758
               11 Hydra digitalis Linnaeus, 1758