Actinie, Coelenterata

Coelenterates are aquatic, mostly marine. The body form is radially symmetrical with - tissue grade of organization. The body has - single opening hypostome surrounded by sensory tentacles leading into - spacious cavity called the gastrovascular cavity or coelenteron. Digestion is both intracellular and extracellular. Respiration and excretion are accomplished by simple diffusion. - network of nerves is spread throughout the body. Many forms exhibit polymorphism, wherein different types of individuals are present in - colony for different functions. These individuals are called Zooids. These animals generally reproduce asexually by budding, though sexual reproduction does occur in some groups.