When the colony was alive, a polyp with numerous tentacles occupied each of the chambers, called hydrotheca.
2.
The about 1, 900 species of Leptomedusae are characterized by a number of features : Their polyps are always living in colonies with the hydranths set in hydrotheca which are usually permanent and often long enough so the animal can fully retract into it; some have very reduced hydrothecae resembling Anthomedusae.