An independent polyp capable of feeding itself: An autozooid is a completely formed alcyonarian zooid and is different when compared to a siphonozooid.

A "polyp" is described as a cylindrical organism with a thin body-wall consisting of two single layers of cells, the "ectoderm" and the "endoderm" separated by a gelatinous noncellular layer or "mesogloea".

At one end there may be a mouth which is usually surrounded by tentacles. Polyps may be single (e.g, "hydra") or colonial (e.g. the coral-forming organisms). The latter are formed by repeated budding from a parent polyp.

In such colonies a tube or "coenosarc" links the body-cavities of all the individuals with one another. There may be many different kinds of polyps in a colony, each specialized for some different function, such as feeding, reproduction, protecting, etc.