(I) The polyp (hydropolyp) is of simple structure, typically much longer than broad, without ectodermal oesophagus or mesenteries, such as are seen in the anthopolyp (see article Anthozoa); the mouth is usually raised above the peristome on a short conical elevation or hypostome; the ectoderm is without cilia.
On the upper face of the hydranth the crown of tentacles (t) surrounds the peristome, from which rises the conical hypostome, bearing the mouth at its extremity.
The hypostome of the hydropolyp may be small, or, on the other hand, as in Eudendrium (Allman, loc. cit.
Hypostome, bearing mouth at its extremity.
The parasitic actinula is found attached to the proboscis of the medusa; it thrusts its greatly elongated hypostome into the mouth of the medusa and nourishes itself upon the food in the digestive cavity of its host.
How would you define hypostome? Add your definition here.