“touch plate” which is situated near the spot-ocellus, tilt and gravity during the jellies' movements pulls downward on the dense lithocyst, which bends the entire rhopalial body such that the cells of the touch plate are either distant from or making contact with the lithocyst hood; this physical mechanism is how the rhopalia deduct sensory information into gravity-sensate behavioral responses As cnidarians lack centralized ganglia and cephalization, the centralization of sensory mechanisms divided up among connections within the rhopalial centers is the nearest concept to a brain that we can place within the phylum. While rhopalia are minute and separated by number and distance across the body, they are extraordinary in the variability of sensory cells they possess in such small areas of tissue. The RNS (rhopalial nervous system) consists of roughly 1000 neurons, excluding photoreceptive cells, and possesses a neuropil, a tightly bundled cluster of cells at its center, serving as the junctions of synapse between adjacent rhopalia. In its totality, the rhopalial nervous system is involved in deduction of the sensation of light (the complexity of which approaches visual processing in some species) and in spatial-behavioral control; because the sensory cells of both sight and physical touch are located within such proximity, studies have explored how related and potentially integral these two mechanisms are to one another in terms of cnidarian behavior. It has thus been observed that the rate of muscle contraction and swimming speed increases when adult Aurelia medusae are exposed to higher levels of light. Additionally that this positive phototactic behavior is absent when the same conditions are presented to jellies whose pigment-cup ocelli have removed (but not the spot-ocellus), insinuating that the pigment-cup ocellus on the oral side is primarily photosensory yet intrinsically related to normal functional behavior In recent years, it has been found that rhopalia retain a sizable reservoir of undifferentiated, stem-like cells, which are though to be poised for potential use in both cell turnover and regeneration in the rhopalia. Formation during metamorphosis Rhopalia are exclusive to the medusoid form of the cnidarian life cycle; young jellies within the classes Schyphozoa and Cubozoa develop through their planula larval and polyp stages lacking these structures. This indicates not only that jellies must employ different sensory mechanisms than those offered by rhopalia before entering the medusa stage, but that the formation of these complex structures takes place completely within the stages of adult