Nematodes are _________.

Coelom is a true internal body cavity between body wall and gut of many animals in which well developed organs can be accommodated. Based on the coelom, animals are divided into following types: Acoelomate: An organism with no cavity or coelom between its digestive tract and outer wall. For example, flatworms and jelly fish. Pseudocoelomate: (Pseudo - false, coelom - body cavity). Nematode is an example of pseudocoelomate. The nematode body is simple and cylindrical rather than flattened. There are tissues, but no real organs, although a type of body cavity is present, which is known as pseudocoelom. For example, Ascaris (roundworm), Wuchereria. Coelomate: Animals with true body cavity. For example, annelida, mollusca, arthropoda, chordata, echinodermata.  Haemocoleomate: 'Haem' means 'iron' (present in blood) and 'coelom' means cavity. When the coelomic cavity is filled by blood, it is known as haemocoelom. For example, arthropoda. In arthropod, there is an open circulatory system and so the blood does not flow in well-defined blood vessels (capillary through which blood flows).