How is the reflex carried out in coelenterates? give examples.

The representative of the type of coelenterates is the freshwater hydra. It is in her that the nervous system appears for the first time – a diffuse reticular type. The reaction to a stimulus is expressed in the excitation of nerve cells, transmission of a nerve impulse and stimulation of skin-muscle cells, followed by their contraction. For example, if a hydra is pricked with a needle, it will shrink into a ball.