A nerve net is a diffuse network of cells that can congregate to form ganglia in some organisms, but does not constitute a brain. In terms of studying nerve nets, Hydra are an ideal class of Cnidaria to research and on which to run tests. Reasons why they are popular model organisms include the following: their nerve nets have a simple pattern to follow, they have a high rate of regeneration, and they are easy to manipulate in experimental procedures.