Cnidarian biology

one of two forms found in the phylum Cnidaria (zoology)

A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species and some species of Ctenophores, which are not closely related to cnidarians. Some groups of Nemerteans also produce larvae that are very similar to the planula, which are called planuliform larva. In a few cnidarian clades, like Aplanulata and the parasitic Myxozoa, the planula larval stage has been lost.

primary organ of digestion and circulation in cnidarians and platyhelminths

Morphallaxis is the regeneration of specific tissue in a variety of organisms due to loss or death of the existing tissue. The word comes from the Greek allazein, (αλλάζειν) which means to change.

stinging filament