Nervous system
Jellyfish, comb jellies, and related animals have diffuse nerve nets rather than a central nervous system. In most jellyfish the nerve net is spread more or less evenly across the body; in comb jellies it is concentrated near the mouth. The nerve nets consist of sensory neurons, which pick up chemical, tactile, and visual signals; motor neurons, which can activate contractions of the body wall; and intermediate neurons, which detect patterns of activity in the sensory neurons and, in response, send signals to groups of motor neurons. In some cases groups of intermediate neurons are clustered into discrete ganglia.
Scaly-foot gastropod
The nervous system is large, and the brain is a solid neural mass without ganglia. The nervous system is reduced in complexity and enlarged in size compared to other neomphaline taxa. As is typical of gastropods, the nervous system is composed of an anterior oesophageal nerve ring and two pairs of longitudinal nerve cords, the ventral pair innervating the foot and the dorsal pair forming a twist via streptoneury. The frontal part of the oesophageal nerve ring is large, connecting two lateral swellings. The huge fused neural mass is directly adjacent to, and passes through, the oeosophageal gland, where the bacteria are housed. There are large tentacular nerves projecting into the cephalic tentacles. The sensory organs of the scaly-foot gastropod include statocysts surrounded by the oesophageal gland, each statocyst with a single statolith. There are also sensory ctenidial bursicles on the tip of the gill filaments; these are known to be present in most vetigastropods, and are present some neomphalines.