| Englisch | Englisch Hydractinia echinata represents one of the few hydroids the embryogenesis and metamorphosis of which can easily be induced and observed. The sexual products mature within the gonophores of specialized gonozooids and are shed into the open water in the morning after illumination. Cleavage is toal, equal, and pseudospiral, and gives rise to morulae which expand to ciliated planulae. The metamorphosis of the planulae into primary polyps can be induced by application of certain bacteria or of a Cs+-pulse. The spindle-shaped larva shortens by muscular contraction and acquires a discshaped appearance. The apical part of the convex disc emerges to form the hydrant, whereas the basal part growths stolons. |
