Speaking generally, three principal types of hydranth can be distinguished, each with subordinate varieties of form.
As a general rule polyp-buds are produced from the hydrorhiza and hydrocaulus, while medusa-buds are formed on the hydranth.
hydranth more shortened, daisy-like in form, with two whorls of tentacles, oral and aboral.
hydranth with tentacles reduced below four; type of Lar (fig. 11), Monobrachium, &c.
In both cases the hydranth is extremely reduced and has no tentacles, and the polyp forms a colony by budding from the base.