Axinella: A genus of SPONGES in the family Axinellidae, comprised of a choanosomal skeleton differentiated in the axial and extra-axial region. The type species is Axinella polypoides.Porifera: The phylum of sponges which are sessile, suspension-feeding, multicellular animals that utilize flagellated cells called choanocytes to circulate water. Most are hermaphroditic. They are probably an early evolutionary side branch that gave rise to no other group of animals. Except for about 150 freshwater species, sponges are marine animals. They are a source of ALKALOIDS; STEROLS; and other complex molecules useful in medicine and biological research.