Bryozoans are minute animals that form flat or branching colonies, often encrusting rocks or objects in the sea, giving them the common name 'sea mosses'. These small colonial creatures, although widespread in marine environments, are often overlooked, and only the larger conspicuous colonies are easily seen. The individual animals, called zooids, are only about 1mm long. The zooids live in a hard case, which protects their soft body parts. Although they lack a head, they feed via a crown of tentacles covered with hair-like cilia that draw food-laden water into their mouths. Not all zooids are feeders: some are modified for attachment, or protection, while others may be modified for the care of developing embryos. Bryozoan colonies grow by asexual budding of new zooids, while new colonies develop from larvae resulting from sexual reproduction. Zooids may be hermaphrodites, while some species have separate male or female zooids.