The gonotheca is formed in its early stage in the same way as the hydrotheca, but the remains of the hydranth persists as an operculum closing the capsule, to be withdrawn when the medusae or genital products are set free (fig.
Numerous medusae are budded successively within the gonotheca and set free; they swim off and mature in the open sea (Allman , p. 48, figs.
Medusae, so-called " meconidia," are budded but not liberated; each in turn, when it reaches sexual maturity, is protruded from the gonotheca by elongation of the stalk, and sets free the embryos, after which it withers and is replaced by another (Allman , p. 57, fig.
Through the gonotheca (fig.
The spadix forms a gelatinous cyst, the so-called acrocyst (ac), external to the gonotheca (gth), enclosing and protecting the embryos.
- Diagrams to show the mode of formation of the Hydrotheca and Gonotheca in Calyptoblastic Hydroids.
A-D are stages common to both; from D arises the hydrotheca (E) or the gonotheca (F); th, theca; st, stomach; 1, tentacles; m, mouth; mb, medusa-buds.
In A two medusa-buds are seen within the gonotheca (gth), the upper more advanced than the lower one.