Entoprocta is a phylum of mostly sessile（英语：Sessility (zoology)） aquatic animals, ranging from 0.1 to 7 millimetres (0.0039 to 0.28 in) long. Mature individuals are goblet（英语：goblet）-shaped, on relatively long stalks. They have a "crown" of solid tentacles whose cilia generate water currents that draw food particles（英语：filter feeder） towards the mouth, and both the mouth and anus lie inside the "crown". The superficially similar Bryozoa (Ectoprocta) have the anus outside a "crown" of hollow tentacles. Most families of entoprocts are colonial, and all but 2 of the 150 species are marine. A few solitary species can move slowly. Some species eject unfertilized ova into the water while others keep their ova in brood chambers until they hatch, and some of these species use placenta-like organs to nourish the developing eggs. After hatching, the larvae swim for a short time and then settle on a surface. There they metamorphose, and the larval gut generally rotates by up to 180°, so that the mouth and anus face upwards. Both colonial and solitary species also reproduce by cloning — solitary species grow clones in the space between the tentacles and then release them when developed, while colonial ones produce new members from the stalks or from corridor-like stolon（英语：stolon）s. Some species of nudibranchs ("sea slugs") and turbellarian flatworms prey on entoprocts. A few entoproct species have been found living in close association with other animals. It is uncertain whether any are invasive species.