The lower part of the pennatulacean colony, lacking polyps or polyp-leaves.
The (gastric) peduncle of a hydromedusa is situated centrally beneath the bell, and is formed around a cone-shaped (hollow) thickening of the mesoglea (jelly) together with associated epidermal and gastrodermal layers, projecting downwards. It is essentially non-contractile, unlike the contractile manubrium. Its length ranges from virtually absent to considerably elongate, in some projecting beyond the bell. The manubrium is attached to its lower end, and above it is the stomach.