In some cases both free medusae and gonophores may be produced from the same hydroid colony.
In other cases, however, the medusa-individuals become sexually mature while still attached to the parent polyp, and are then not set free at all, but become appanages of the hydroid colony and undergo degenerative changes leading to reduction and even to complete obliteration of their original medusan structure.
Hydra is, moreover, bisexual, in contrast with what is known of hydroid colonies.
Common genera are the hydroid Bougainvillea (figs.
Moreover, all the medusae budded from a given hydroid colony are either male or female, so that even the non-sexual polyp must be considered to have a latent sex.
The hydroid phase, if any, is not known.
I, End of hydroid of the thalloid Liverwort Blyttia, showing the thick lignified wall penetrated by simple pits.
T his common British hydroid belongs by its characters to the family Bougainvillidae; it produces, however, a medusa of the genusTiara (fig.
The hydroid genus Lafoea is remarkable for producing gonothecae on the hydrorhiza, each containing a blastostyle which bears a single gonophore; this portion of the colony was formerly regarded as an independent parasitic hydroid, and was named Coppinia.
The British genus Gemmaria, however, is budded from a hydroid referable to the family Corynidae.